png.c

/* png.c - location for general purpose libpng functions * * Copyright (c) 2018-2020 Cosmin Truta * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson * Copyright (c) 1996-1997 Andreas Dilger * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc. * * This code is released under the libpng license. * For conditions of distribution and use, see the disclaimer * and license in png.h */ #include "pngpriv.h" /* Generate a compiler error if there is an old png.h in the search path. */ typedef png_libpng_version_1_6_38_git Your_png_h_is_not_version_1_6_38_git; #ifdef __GNUC__ /* The version tests may need to be added to, but the problem warning has * consistently been fixed in GCC versions which obtain wide-spread release. * The problem is that many versions of GCC rearrange comparison expressions in * the optimizer in such a way that the results of the comparison will change * if signed integer overflow occurs. Such comparisons are not permitted in * ANSI C90, however GCC isn't clever enough to work out that that do not occur * below in png_ascii_from_fp and png_muldiv, so it produces a warning with * -Wextra. Unfortunately this is highly dependent on the optimizer and the * machine architecture so the warning comes and goes unpredictably and is * impossible to "fix", even were that a good idea. */ #if __GNUC__ == 7 && __GNUC_MINOR__ == 1 #define GCC_STRICT_OVERFLOW 1 #endif /* GNU 7.1.x */ #endif /* GNU */ #ifndef GCC_STRICT_OVERFLOW #define GCC_STRICT_OVERFLOW 0 #endif /* Tells libpng that we have already handled the first "num_bytes" bytes * of the PNG file signature. If the PNG data is embedded into another * stream we can set num_bytes = 8 so that libpng will not attempt to read * or write any of the magic bytes before it starts on the IHDR. */ #ifdef PNG_READ_SUPPORTED void PNGAPI png_set_sig_bytes(png_structrp png_ptr, int num_bytes) { unsigned int nb = (unsigned int)num_bytes; png_debug(1, "in png_set_sig_bytes"); if (png_ptr == NULL) return; if (num_bytes < 0) nb = 0; if (nb > 8) png_error(png_ptr, "Too many bytes for PNG signature"); png_ptr->sig_bytes = (png_byte)nb; } /* Checks whether the supplied bytes match the PNG signature. We allow * checking less than the full 8-byte signature so that those apps that * already read the first few bytes of a file to determine the file type * can simply check the remaining bytes for extra assurance. Returns * an integer less than, equal to, or greater than zero if sig is found, * respectively, to be less than, to match, or be greater than the correct * PNG signature (this is the same behavior as strcmp, memcmp, etc). */ int PNGAPI png_sig_cmp(png_const_bytep sig, size_t start, size_t num_to_check) { png_byte png_signature[8] = {137, 80, 78, 71, 13, 10, 26, 10}; if (num_to_check > 8) num_to_check = 8; else if (num_to_check < 1) return (-1); if (start > 7) return (-1); if (start + num_to_check > 8) num_to_check = 8 - start; return ((int)(memcmp(&sig[start], &png_signature[start], num_to_check))); } #endif /* READ */ #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) /* Function to allocate memory for zlib */ PNG_FUNCTION(voidpf /* PRIVATE */, png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED) { png_alloc_size_t num_bytes = size; if (png_ptr == NULL) return NULL; if (items >= (~(png_alloc_size_t)0)/size) { png_warning (png_voidcast(png_structrp, png_ptr), "Potential overflow in png_zalloc()"); return NULL; } num_bytes *= items; return png_malloc_warn(png_voidcast(png_structrp, png_ptr), num_bytes); } /* Function to free memory for zlib */ void /* PRIVATE */ png_zfree(voidpf png_ptr, voidpf ptr) { png_free(png_voidcast(png_const_structrp,png_ptr), ptr); } /* Reset the CRC variable to 32 bits of 1's. Care must be taken * in case CRC is > 32 bits to leave the top bits 0. */ void /* PRIVATE */ png_reset_crc(png_structrp png_ptr) { /* The cast is safe because the crc is a 32-bit value. */ png_ptr->crc = (png_uint_32)crc32(0, Z_NULL, 0); } /* Calculate the CRC over a section of data. We can only pass as * much data to this routine as the largest single buffer size. We * also check that this data will actually be used before going to the * trouble of calculating it. */ void /* PRIVATE */ png_calculate_crc(png_structrp png_ptr, png_const_bytep ptr, size_t length) { int need_crc = 1; if (PNG_CHUNK_ANCILLARY(png_ptr->chunk_name) != 0) { if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) == (PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN)) need_crc = 0; } else /* critical */ { if ((png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) != 0) need_crc = 0; } /* 'uLong' is defined in zlib.h as unsigned long; this means that on some * systems it is a 64-bit value. crc32, however, returns 32 bits so the * following cast is safe. 'uInt' may be no more than 16 bits, so it is * necessary to perform a loop here. */ if (need_crc != 0 && length > 0) { uLong crc = png_ptr->crc; /* Should never issue a warning */ do { uInt safe_length = (uInt)length; #ifndef __COVERITY__ if (safe_length == 0) safe_length = (uInt)-1; /* evil, but safe */ #endif crc = crc32(crc, ptr, safe_length); /* The following should never issue compiler warnings; if they do the * target system has characteristics that will probably violate other * assumptions within the libpng code. */ ptr += safe_length; length -= safe_length; } while (length > 0); /* And the following is always safe because the crc is only 32 bits. */ png_ptr->crc = (png_uint_32)crc; } } /* Check a user supplied version number, called from both read and write * functions that create a png_struct. */ int png_user_version_check(png_structrp png_ptr, png_const_charp user_png_ver) { /* Libpng versions 1.0.0 and later are binary compatible if the version * string matches through the second '.'; we must recompile any * applications that use any older library version. */ if (user_png_ver != NULL) { int i = -1; int found_dots = 0; do { i++; if (user_png_ver[i] != PNG_LIBPNG_VER_STRING[i]) png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH; if (user_png_ver[i] == '.') found_dots++; } while (found_dots < 2 && user_png_ver[i] != 0 && PNG_LIBPNG_VER_STRING[i] != 0); } else png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH; if ((png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH) != 0) { #ifdef PNG_WARNINGS_SUPPORTED size_t pos = 0; char m[128]; pos = png_safecat(m, (sizeof m), pos, "Application built with libpng-"); pos = png_safecat(m, (sizeof m), pos, user_png_ver); pos = png_safecat(m, (sizeof m), pos, " but running with "); pos = png_safecat(m, (sizeof m), pos, PNG_LIBPNG_VER_STRING); PNG_UNUSED(pos) png_warning(png_ptr, m); #endif #ifdef PNG_ERROR_NUMBERS_SUPPORTED png_ptr->flags = 0; #endif return 0; } /* Success return. */ return 1; } /* Generic function to create a png_struct for either read or write - this * contains the common initialization. */ PNG_FUNCTION(png_structp /* PRIVATE */, png_create_png_struct,(png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr, png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED) { png_struct create_struct; # ifdef PNG_SETJMP_SUPPORTED jmp_buf create_jmp_buf; # endif /* This temporary stack-allocated structure is used to provide a place to * build enough context to allow the user provided memory allocator (if any) * to be called. */ memset(&create_struct, 0, (sizeof create_struct)); /* Added at libpng-1.2.6 */ # ifdef PNG_USER_LIMITS_SUPPORTED create_struct.user_width_max = PNG_USER_WIDTH_MAX; create_struct.user_height_max = PNG_USER_HEIGHT_MAX; # ifdef PNG_USER_CHUNK_CACHE_MAX /* Added at libpng-1.2.43 and 1.4.0 */ create_struct.user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX; # endif # ifdef PNG_USER_CHUNK_MALLOC_MAX /* Added at libpng-1.2.43 and 1.4.1, required only for read but exists * in png_struct regardless. */ create_struct.user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX; # endif # endif /* The following two API calls simply set fields in png_struct, so it is safe * to do them now even though error handling is not yet set up. */ # ifdef PNG_USER_MEM_SUPPORTED png_set_mem_fn(&create_struct, mem_ptr, malloc_fn, free_fn); # else PNG_UNUSED(mem_ptr) PNG_UNUSED(malloc_fn) PNG_UNUSED(free_fn) # endif /* (*error_fn) can return control to the caller after the error_ptr is set, * this will result in a memory leak unless the error_fn does something * extremely sophisticated. The design lacks merit but is implicit in the * API. */ png_set_error_fn(&create_struct, error_ptr, error_fn, warn_fn); # ifdef PNG_SETJMP_SUPPORTED if (!setjmp(create_jmp_buf)) # endif { # ifdef PNG_SETJMP_SUPPORTED /* Temporarily fake out the longjmp information until we have * successfully completed this function. This only works if we have * setjmp() support compiled in, but it is safe - this stuff should * never happen. */ create_struct.jmp_buf_ptr = &create_jmp_buf; create_struct.jmp_buf_size = 0; /*stack allocation*/ create_struct.longjmp_fn = longjmp; # endif /* Call the general version checker (shared with read and write code): */ if (png_user_version_check(&create_struct, user_png_ver) != 0) { png_structrp png_ptr = png_voidcast(png_structrp, png_malloc_warn(&create_struct, (sizeof *png_ptr))); if (png_ptr != NULL) { /* png_ptr->zstream holds a back-pointer to the png_struct, so * this can only be done now: */ create_struct.zstream.zalloc = png_zalloc; create_struct.zstream.zfree = png_zfree; create_struct.zstream.opaque = png_ptr; # ifdef PNG_SETJMP_SUPPORTED /* Eliminate the local error handling: */ create_struct.jmp_buf_ptr = NULL; create_struct.jmp_buf_size = 0; create_struct.longjmp_fn = 0; # endif *png_ptr = create_struct; /* This is the successful return point */ return png_ptr; } } } /* A longjmp because of a bug in the application storage allocator or a * simple failure to allocate the png_struct. */ return NULL; } /* Allocate the memory for an info_struct for the application. */ PNG_FUNCTION(png_infop,PNGAPI png_create_info_struct,(png_const_structrp png_ptr),PNG_ALLOCATED) { png_inforp info_ptr; png_debug(1, "in png_create_info_struct"); if (png_ptr == NULL) return NULL; /* Use the internal API that does not (or at least should not) error out, so * that this call always returns ok. The application typically sets up the * error handling *after* creating the info_struct because this is the way it * has always been done in 'example.c'. */ info_ptr = png_voidcast(png_inforp, png_malloc_base(png_ptr, (sizeof *info_ptr))); if (info_ptr != NULL) memset(info_ptr, 0, (sizeof *info_ptr)); return info_ptr; } /* This function frees the memory associated with a single info struct. * Normally, one would use either png_destroy_read_struct() or * png_destroy_write_struct() to free an info struct, but this may be * useful for some applications. From libpng 1.6.0 this function is also used * internally to implement the png_info release part of the 'struct' destroy * APIs. This ensures that all possible approaches free the same data (all of * it). */ void PNGAPI png_destroy_info_struct(png_const_structrp png_ptr, png_infopp info_ptr_ptr) { png_inforp info_ptr = NULL; png_debug(1, "in png_destroy_info_struct"); if (png_ptr == NULL) return; if (info_ptr_ptr != NULL) info_ptr = *info_ptr_ptr; if (info_ptr != NULL) { /* Do this first in case of an error below; if the app implements its own * memory management this can lead to png_free calling png_error, which * will abort this routine and return control to the app error handler. * An infinite loop may result if it then tries to free the same info * ptr. */ *info_ptr_ptr = NULL; png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1); memset(info_ptr, 0, (sizeof *info_ptr)); png_free(png_ptr, info_ptr); } } /* Initialize the info structure. This is now an internal function (0.89) * and applications using it are urged to use png_create_info_struct() * instead. Use deprecated in 1.6.0, internal use removed (used internally it * is just a memset). * * NOTE: it is almost inconceivable that this API is used because it bypasses * the user-memory mechanism and the user error handling/warning mechanisms in * those cases where it does anything other than a memset. */ PNG_FUNCTION(void,PNGAPI png_info_init_3,(png_infopp ptr_ptr, size_t png_info_struct_size), PNG_DEPRECATED) { png_inforp info_ptr = *ptr_ptr; png_debug(1, "in png_info_init_3"); if (info_ptr == NULL) return; if ((sizeof (png_info)) > png_info_struct_size) { *ptr_ptr = NULL; /* The following line is why this API should not be used: */ free(info_ptr); info_ptr = png_voidcast(png_inforp, png_malloc_base(NULL, (sizeof *info_ptr))); if (info_ptr == NULL) return; *ptr_ptr = info_ptr; } /* Set everything to 0 */ memset(info_ptr, 0, (sizeof *info_ptr)); } /* The following API is not called internally */ void PNGAPI png_data_freer(png_const_structrp png_ptr, png_inforp info_ptr, int freer, png_uint_32 mask) { png_debug(1, "in png_data_freer"); if (png_ptr == NULL || info_ptr == NULL) return; if (freer == PNG_DESTROY_WILL_FREE_DATA) info_ptr->free_me |= mask; else if (freer == PNG_USER_WILL_FREE_DATA) info_ptr->free_me &= ~mask; else png_error(png_ptr, "Unknown freer parameter in png_data_freer"); } void PNGAPI png_free_data(png_const_structrp png_ptr, png_inforp info_ptr, png_uint_32 mask, int num) { png_debug(1, "in png_free_data"); if (png_ptr == NULL || info_ptr == NULL) return; #ifdef PNG_TEXT_SUPPORTED /* Free text item num or (if num == -1) all text items */ if (info_ptr->text != NULL && ((mask & PNG_FREE_TEXT) & info_ptr->free_me) != 0) { if (num != -1) { png_free(png_ptr, info_ptr->text[num].key); info_ptr->text[num].key = NULL; } else { int i; for (i = 0; i < info_ptr->num_text; i++) png_free(png_ptr, info_ptr->text[i].key); png_free(png_ptr, info_ptr->text); info_ptr->text = NULL; info_ptr->num_text = 0; info_ptr->max_text = 0; } } #endif #ifdef PNG_tRNS_SUPPORTED /* Free any tRNS entry */ if (((mask & PNG_FREE_TRNS) & info_ptr->free_me) != 0) { info_ptr->valid &= ~PNG_INFO_tRNS; png_free(png_ptr, info_ptr->trans_alpha); info_ptr->trans_alpha = NULL; info_ptr->num_trans = 0; } #endif #ifdef PNG_sCAL_SUPPORTED /* Free any sCAL entry */ if (((mask & PNG_FREE_SCAL) & info_ptr->free_me) != 0) { png_free(png_ptr, info_ptr->scal_s_width); png_free(png_ptr, info_ptr->scal_s_height); info_ptr->scal_s_width = NULL; info_ptr->scal_s_height = NULL; info_ptr->valid &= ~PNG_INFO_sCAL; } #endif #ifdef PNG_pCAL_SUPPORTED /* Free any pCAL entry */ if (((mask & PNG_FREE_PCAL) & info_ptr->free_me) != 0) { png_free(png_ptr, info_ptr->pcal_purpose); png_free(png_ptr, info_ptr->pcal_units); info_ptr->pcal_purpose = NULL; info_ptr->pcal_units = NULL; if (info_ptr->pcal_params != NULL) { int i; for (i = 0; i < info_ptr->pcal_nparams; i++) png_free(png_ptr, info_ptr->pcal_params[i]); png_free(png_ptr, info_ptr->pcal_params); info_ptr->pcal_params = NULL; } info_ptr->valid &= ~PNG_INFO_pCAL; } #endif #ifdef PNG_iCCP_SUPPORTED /* Free any profile entry */ if (((mask & PNG_FREE_ICCP) & info_ptr->free_me) != 0) { png_free(png_ptr, info_ptr->iccp_name); png_free(png_ptr, info_ptr->iccp_profile); info_ptr->iccp_name = NULL; info_ptr->iccp_profile = NULL; info_ptr->valid &= ~PNG_INFO_iCCP; } #endif #ifdef PNG_sPLT_SUPPORTED /* Free a given sPLT entry, or (if num == -1) all sPLT entries */ if (info_ptr->splt_palettes != NULL && ((mask & PNG_FREE_SPLT) & info_ptr->free_me) != 0) { if (num != -1) { png_free(png_ptr, info_ptr->splt_palettes[num].name); png_free(png_ptr, info_ptr->splt_palettes[num].entries); info_ptr->splt_palettes[num].name = NULL; info_ptr->splt_palettes[num].entries = NULL; } else { int i; for (i = 0; i < info_ptr->splt_palettes_num; i++) { png_free(png_ptr, info_ptr->splt_palettes[i].name); png_free(png_ptr, info_ptr->splt_palettes[i].entries); } png_free(png_ptr, info_ptr->splt_palettes); info_ptr->splt_palettes = NULL; info_ptr->splt_palettes_num = 0; info_ptr->valid &= ~PNG_INFO_sPLT; } } #endif #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED if (info_ptr->unknown_chunks != NULL && ((mask & PNG_FREE_UNKN) & info_ptr->free_me) != 0) { if (num != -1) { png_free(png_ptr, info_ptr->unknown_chunks[num].data); info_ptr->unknown_chunks[num].data = NULL; } else { int i; for (i = 0; i < info_ptr->unknown_chunks_num; i++) png_free(png_ptr, info_ptr->unknown_chunks[i].data); png_free(png_ptr, info_ptr->unknown_chunks); info_ptr->unknown_chunks = NULL; info_ptr->unknown_chunks_num = 0; } } #endif #ifdef PNG_eXIf_SUPPORTED /* Free any eXIf entry */ if (((mask & PNG_FREE_EXIF) & info_ptr->free_me) != 0) { # ifdef PNG_READ_eXIf_SUPPORTED if (info_ptr->eXIf_buf) { png_free(png_ptr, info_ptr->eXIf_buf); info_ptr->eXIf_buf = NULL; } # endif if (info_ptr->exif) { png_free(png_ptr, info_ptr->exif); info_ptr->exif = NULL; } info_ptr->valid &= ~PNG_INFO_eXIf; } #endif #ifdef PNG_hIST_SUPPORTED /* Free any hIST entry */ if (((mask & PNG_FREE_HIST) & info_ptr->free_me) != 0) { png_free(png_ptr, info_ptr->hist); info_ptr->hist = NULL; info_ptr->valid &= ~PNG_INFO_hIST; } #endif /* Free any PLTE entry that was internally allocated */ if (((mask & PNG_FREE_PLTE) & info_ptr->free_me) != 0) { png_free(png_ptr, info_ptr->palette); info_ptr->palette = NULL; info_ptr->valid &= ~PNG_INFO_PLTE; info_ptr->num_palette = 0; } #ifdef PNG_INFO_IMAGE_SUPPORTED /* Free any image bits attached to the info structure */ if (((mask & PNG_FREE_ROWS) & info_ptr->free_me) != 0) { if (info_ptr->row_pointers != NULL) { png_uint_32 row; for (row = 0; row < info_ptr->height; row++) png_free(png_ptr, info_ptr->row_pointers[row]); png_free(png_ptr, info_ptr->row_pointers); info_ptr->row_pointers = NULL; } info_ptr->valid &= ~PNG_INFO_IDAT; } #endif if (num != -1) mask &= ~PNG_FREE_MUL; info_ptr->free_me &= ~mask; } #endif /* READ || WRITE */ /* This function returns a pointer to the io_ptr associated with the user * functions. The application should free any memory associated with this * pointer before png_write_destroy() or png_read_destroy() are called. */ png_voidp PNGAPI png_get_io_ptr(png_const_structrp png_ptr) { if (png_ptr == NULL) return (NULL); return (png_ptr->io_ptr); } #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) # ifdef PNG_STDIO_SUPPORTED /* Initialize the default input/output functions for the PNG file. If you * use your own read or write routines, you can call either png_set_read_fn() * or png_set_write_fn() instead of png_init_io(). If you have defined * PNG_NO_STDIO or otherwise disabled PNG_STDIO_SUPPORTED, you must use a * function of your own because "FILE *" isn't necessarily available. */ void PNGAPI png_init_io(png_structrp png_ptr, png_FILE_p fp) { png_debug(1, "in png_init_io"); if (png_ptr == NULL) return; png_ptr->io_ptr = (png_voidp)fp; } # endif # ifdef PNG_SAVE_INT_32_SUPPORTED /* PNG signed integers are saved in 32-bit 2's complement format. ANSI C-90 * defines a cast of a signed integer to an unsigned integer either to preserve * the value, if it is positive, or to calculate: * * (UNSIGNED_MAX+1) + integer * * Where UNSIGNED_MAX is the appropriate maximum unsigned value, so when the * negative integral value is added the result will be an unsigned value * correspnding to the 2's complement representation. */ void PNGAPI png_save_int_32(png_bytep buf, png_int_32 i) { png_save_uint_32(buf, (png_uint_32)i); } # endif # ifdef PNG_TIME_RFC1123_SUPPORTED /* Convert the supplied time into an RFC 1123 string suitable for use in * a "Creation Time" or other text-based time string. */ int PNGAPI png_convert_to_rfc1123_buffer(char out[29], png_const_timep ptime) { static const char short_months[12][4] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"}; if (out == NULL) return 0; if (ptime->year > 9999 /* RFC1123 limitation */ || ptime->month == 0 || ptime->month > 12 || ptime->day == 0 || ptime->day > 31 || ptime->hour > 23 || ptime->minute > 59 || ptime->second > 60) return 0; { size_t pos = 0; char number_buf[5]; /* enough for a four-digit year */ # define APPEND_STRING(string) pos = png_safecat(out, 29, pos, (string)) # define APPEND_NUMBER(format, value)\ APPEND_STRING(PNG_FORMAT_NUMBER(number_buf, format, (value))) # define APPEND(ch) if (pos < 28) out[pos++] = (ch) APPEND_NUMBER(PNG_NUMBER_FORMAT_u, (unsigned)ptime->day); APPEND(' '); APPEND_STRING(short_months[(ptime->month - 1)]); APPEND(' '); APPEND_NUMBER(PNG_NUMBER_FORMAT_u, ptime->year); APPEND(' '); APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->hour); APPEND(':'); APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->minute); APPEND(':'); APPEND_NUMBER(PNG_NUMBER_FORMAT_02u, (unsigned)ptime->second); APPEND_STRING(" +0000"); /* This reliably terminates the buffer */ PNG_UNUSED (pos) # undef APPEND # undef APPEND_NUMBER # undef APPEND_STRING } return 1; } # if PNG_LIBPNG_VER < 10700 /* To do: remove the following from libpng-1.7 */ /* Original API that uses a private buffer in png_struct. * Deprecated because it causes png_struct to carry a spurious temporary * buffer (png_struct::time_buffer), better to have the caller pass this in. */ png_const_charp PNGAPI png_convert_to_rfc1123(png_structrp png_ptr, png_const_timep ptime) { if (png_ptr != NULL) { /* The only failure above if png_ptr != NULL is from an invalid ptime */ if (png_convert_to_rfc1123_buffer(png_ptr->time_buffer, ptime) == 0) png_warning(png_ptr, "Ignoring invalid time value"); else return png_ptr->time_buffer; } return NULL; } # endif /* LIBPNG_VER < 10700 */ # endif /* TIME_RFC1123 */ #endif /* READ || WRITE */ png_const_charp PNGAPI png_get_copyright(png_const_structrp png_ptr) { PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */ #ifdef PNG_STRING_COPYRIGHT return PNG_STRING_COPYRIGHT #else return PNG_STRING_NEWLINE \ "libpng version 1.6.38.git" PNG_STRING_NEWLINE \ "Copyright (c) 2018-2020 Cosmin Truta" PNG_STRING_NEWLINE \ "Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson" \ PNG_STRING_NEWLINE \ "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \ "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \ PNG_STRING_NEWLINE; #endif } /* The following return the library version as a short string in the * format 1.0.0 through 99.99.99zz. To get the version of *.h files * used with your application, print out PNG_LIBPNG_VER_STRING, which * is defined in png.h. * Note: now there is no difference between png_get_libpng_ver() and * png_get_header_ver(). Due to the version_nn_nn_nn typedef guard, * it is guaranteed that png.c uses the correct version of png.h. */ png_const_charp PNGAPI png_get_libpng_ver(png_const_structrp png_ptr) { /* Version of *.c files used when building libpng */ return png_get_header_ver(png_ptr); } png_const_charp PNGAPI png_get_header_ver(png_const_structrp png_ptr) { /* Version of *.h files used when building libpng */ PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */ return PNG_LIBPNG_VER_STRING; } png_const_charp PNGAPI png_get_header_version(png_const_structrp png_ptr) { /* Returns longer string containing both version and date */ PNG_UNUSED(png_ptr) /* Silence compiler warning about unused png_ptr */ #ifdef __STDC__ return PNG_HEADER_VERSION_STRING # ifndef PNG_READ_SUPPORTED " (NO READ SUPPORT)" # endif PNG_STRING_NEWLINE; #else return PNG_HEADER_VERSION_STRING; #endif } #ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED /* NOTE: this routine is not used internally! */ /* Build a grayscale palette. Palette is assumed to be 1 << bit_depth * large of png_color. This lets grayscale images be treated as * paletted. Most useful for gamma correction and simplification * of code. This API is not used internally. */ void PNGAPI png_build_grayscale_palette(int bit_depth, png_colorp palette) { int num_palette; int color_inc; int i; int v; png_debug(1, "in png_do_build_grayscale_palette"); if (palette == NULL) return; switch (bit_depth) { case 1: num_palette = 2; color_inc = 0xff; break; case 2: num_palette = 4; color_inc = 0x55; break; case 4: num_palette = 16; color_inc = 0x11; break; case 8: num_palette = 256; color_inc = 1; break; default: num_palette = 0; color_inc = 0; break; } for (i = 0, v = 0; i < num_palette; i++, v += color_inc) { palette[i].red = (png_byte)(v & 0xff); palette[i].green = (png_byte)(v & 0xff); palette[i].blue = (png_byte)(v & 0xff); } } #endif #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED int PNGAPI png_handle_as_unknown(png_const_structrp png_ptr, png_const_bytep chunk_name) { /* Check chunk_name and return "keep" value if it's on the list, else 0 */ png_const_bytep p, p_end; if (png_ptr == NULL || chunk_name == NULL || png_ptr->num_chunk_list == 0) return PNG_HANDLE_CHUNK_AS_DEFAULT; p_end = png_ptr->chunk_list; p = p_end + png_ptr->num_chunk_list*5; /* beyond end */ /* The code is the fifth byte after each four byte string. Historically this * code was always searched from the end of the list, this is no longer * necessary because the 'set' routine handles duplicate entries correctly. */ do /* num_chunk_list > 0, so at least one */ { p -= 5; if (memcmp(chunk_name, p, 4) == 0) return p[4]; } while (p > p_end); /* This means that known chunks should be processed and unknown chunks should * be handled according to the value of png_ptr->unknown_default; this can be * confusing because, as a result, there are two levels of defaulting for * unknown chunks. */ return PNG_HANDLE_CHUNK_AS_DEFAULT; } #if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) ||\ defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED) int /* PRIVATE */ png_chunk_unknown_handling(png_const_structrp png_ptr, png_uint_32 chunk_name) { png_byte chunk_string[5]; PNG_CSTRING_FROM_CHUNK(chunk_string, chunk_name); return png_handle_as_unknown(png_ptr, chunk_string); } #endif /* READ_UNKNOWN_CHUNKS || HANDLE_AS_UNKNOWN */ #endif /* SET_UNKNOWN_CHUNKS */ #ifdef PNG_READ_SUPPORTED /* This function, added to libpng-1.0.6g, is untested. */ int PNGAPI png_reset_zstream(png_structrp png_ptr) { if (png_ptr == NULL) return Z_STREAM_ERROR; /* WARNING: this resets the window bits to the maximum! */ return (inflateReset(&png_ptr->zstream)); } #endif /* READ */ /* This function was added to libpng-1.0.7 */ png_uint_32 PNGAPI png_access_version_number(void) { /* Version of *.c files used when building libpng */ return((png_uint_32)PNG_LIBPNG_VER); } #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED) /* Ensure that png_ptr->zstream.msg holds some appropriate error message string. * If it doesn't 'ret' is used to set it to something appropriate, even in cases * like Z_OK or Z_STREAM_END where the error code is apparently a success code. */ void /* PRIVATE */ png_zstream_error(png_structrp png_ptr, int ret) { /* Translate 'ret' into an appropriate error string, priority is given to the * one in zstream if set. This always returns a string, even in cases like * Z_OK or Z_STREAM_END where the error code is a success code. */ if (png_ptr->zstream.msg == NULL) switch (ret) { default: case Z_OK: png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return code"); break; case Z_STREAM_END: /* Normal exit */ png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected end of LZ stream"); break; case Z_NEED_DICT: /* This means the deflate stream did not have a dictionary; this * indicates a bogus PNG. */ png_ptr->zstream.msg = PNGZ_MSG_CAST("missing LZ dictionary"); break; case Z_ERRNO: /* gz APIs only: should not happen */ png_ptr->zstream.msg = PNGZ_MSG_CAST("zlib IO error"); break; case Z_STREAM_ERROR: /* internal libpng error */ png_ptr->zstream.msg = PNGZ_MSG_CAST("bad parameters to zlib"); break; case Z_DATA_ERROR: png_ptr->zstream.msg = PNGZ_MSG_CAST("damaged LZ stream"); break; case Z_MEM_ERROR: png_ptr->zstream.msg = PNGZ_MSG_CAST("insufficient memory"); break; case Z_BUF_ERROR: /* End of input or output; not a problem if the caller is doing * incremental read or write. */ png_ptr->zstream.msg = PNGZ_MSG_CAST("truncated"); break; case Z_VERSION_ERROR: png_ptr->zstream.msg = PNGZ_MSG_CAST("unsupported zlib version"); break; case PNG_UNEXPECTED_ZLIB_RETURN: /* Compile errors here mean that zlib now uses the value co-opted in * pngpriv.h for PNG_UNEXPECTED_ZLIB_RETURN; update the switch above * and change pngpriv.h. Note that this message is "... return", * whereas the default/Z_OK one is "... return code". */ png_ptr->zstream.msg = PNGZ_MSG_CAST("unexpected zlib return"); break; } } /* png_convert_size: a PNGAPI but no longer in png.h, so deleted * at libpng 1.5.5! */ /* Added at libpng version 1.2.34 and 1.4.0 (moved from pngset.c) */ #ifdef PNG_GAMMA_SUPPORTED /* always set if COLORSPACE */ static int png_colorspace_check_gamma(png_const_structrp png_ptr, png_colorspacerp colorspace, png_fixed_point gAMA, int from) /* This is called to check a new gamma value against an existing one. The * routine returns false if the new gamma value should not be written. * * 'from' says where the new gamma value comes from: * * 0: the new gamma value is the libpng estimate for an ICC profile * 1: the new gamma value comes from a gAMA chunk * 2: the new gamma value comes from an sRGB chunk */ { png_fixed_point gtest; if ((colorspace->flags & PNG_COLORSPACE_HAVE_GAMMA) != 0 && (png_muldiv(&gtest, colorspace->gamma, PNG_FP_1, gAMA) == 0 || png_gamma_significant(gtest) != 0)) { /* Either this is an sRGB image, in which case the calculated gamma * approximation should match, or this is an image with a profile and the * value libpng calculates for the gamma of the profile does not match the * value recorded in the file. The former, sRGB, case is an error, the * latter is just a warning. */ if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0 || from == 2) { png_chunk_report(png_ptr, "gamma value does not match sRGB", PNG_CHUNK_ERROR); /* Do not overwrite an sRGB value */ return from == 2; } else /* sRGB tag not involved */ { png_chunk_report(png_ptr, "gamma value does not match libpng estimate", PNG_CHUNK_WARNING); return from == 1; } } return 1; } void /* PRIVATE */ png_colorspace_set_gamma(png_const_structrp png_ptr, png_colorspacerp colorspace, png_fixed_point gAMA) { /* Changed in libpng-1.5.4 to limit the values to ensure overflow can't * occur. Since the fixed point representation is asymmetrical it is * possible for 1/gamma to overflow the limit of 21474 and this means the * gamma value must be at least 5/100000 and hence at most 20000.0. For * safety the limits here are a little narrower. The values are 0.00016 to * 6250.0, which are truly ridiculous gamma values (and will produce * displays that are all black or all white.) * * In 1.6.0 this test replaces the ones in pngrutil.c, in the gAMA chunk * handling code, which only required the value to be >0. */ png_const_charp errmsg; if (gAMA < 16 || gAMA > 625000000) errmsg = "gamma value out of range"; # ifdef PNG_READ_gAMA_SUPPORTED /* Allow the application to set the gamma value more than once */ else if ((png_ptr->mode & PNG_IS_READ_STRUCT) != 0 && (colorspace->flags & PNG_COLORSPACE_FROM_gAMA) != 0) errmsg = "duplicate"; # endif /* Do nothing if the colorspace is already invalid */ else if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0) return; else { if (png_colorspace_check_gamma(png_ptr, colorspace, gAMA, 1/*from gAMA*/) != 0) { /* Store this gamma value. */ colorspace->gamma = gAMA; colorspace->flags |= (PNG_COLORSPACE_HAVE_GAMMA | PNG_COLORSPACE_FROM_gAMA); } /* At present if the check_gamma test fails the gamma of the colorspace is * not updated however the colorspace is not invalidated. This * corresponds to the case where the existing gamma comes from an sRGB * chunk or profile. An error message has already been output. */ return; } /* Error exit - errmsg has been set. */ colorspace->flags |= PNG_COLORSPACE_INVALID; png_chunk_report(png_ptr, errmsg, PNG_CHUNK_WRITE_ERROR); } void /* PRIVATE */ png_colorspace_sync_info(png_const_structrp png_ptr, png_inforp info_ptr) { if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) != 0) { /* Everything is invalid */ info_ptr->valid &= ~(PNG_INFO_gAMA|PNG_INFO_cHRM|PNG_INFO_sRGB| PNG_INFO_iCCP); # ifdef PNG_COLORSPACE_SUPPORTED /* Clean up the iCCP profile now if it won't be used. */ png_free_data(png_ptr, info_ptr, PNG_FREE_ICCP, -1/*not used*/); # else PNG_UNUSED(png_ptr) # endif } else { # ifdef PNG_COLORSPACE_SUPPORTED /* Leave the INFO_iCCP flag set if the pngset.c code has already set * it; this allows a PNG to contain a profile which matches sRGB and * yet still have that profile retrievable by the application. */ if ((info_ptr->colorspace.flags & PNG_COLORSPACE_MATCHES_sRGB) != 0) info_ptr->valid |= PNG_INFO_sRGB; else info_ptr->valid &= ~PNG_INFO_sRGB; if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0) info_ptr->valid |= PNG_INFO_cHRM; else info_ptr->valid &= ~PNG_INFO_cHRM; # endif if ((info_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) != 0) info_ptr->valid |= PNG_INFO_gAMA; else info_ptr->valid &= ~PNG_INFO_gAMA; } } #ifdef PNG_READ_SUPPORTED void /* PRIVATE */ png_colorspace_sync(png_const_structrp png_ptr, png_inforp info_ptr) { if (info_ptr == NULL) /* reduce code size; check here not in the caller */ return; info_ptr->colorspace = png_ptr->colorspace; png_colorspace_sync_info(png_ptr, info_ptr); } #endif #endif /* GAMMA */ #ifdef PNG_COLORSPACE_SUPPORTED /* Added at libpng-1.5.5 to support read and write of true CIEXYZ values for * cHRM, as opposed to using chromaticities. These internal APIs return * non-zero on a parameter error. The X, Y and Z values are required to be * positive and less than 1.0. */ static int png_xy_from_XYZ(png_xy *xy, const png_XYZ *XYZ) { png_int_32 d, dwhite, whiteX, whiteY; d = XYZ->red_X + XYZ->red_Y + XYZ->red_Z; if (png_muldiv(&xy->redx, XYZ->red_X, PNG_FP_1, d) == 0) return 1; if (png_muldiv(&xy->redy, XYZ->red_Y, PNG_FP_1, d) == 0) return 1; dwhite = d; whiteX = XYZ->red_X; whiteY = XYZ->red_Y; d = XYZ->green_X + XYZ->green_Y + XYZ->green_Z; if (png_muldiv(&xy->greenx, XYZ->green_X, PNG_FP_1, d) == 0) return 1; if (png_muldiv(&xy->greeny, XYZ->green_Y, PNG_FP_1, d) == 0) return 1; dwhite += d; whiteX += XYZ->green_X; whiteY += XYZ->green_Y; d = XYZ->blue_X + XYZ->blue_Y + XYZ->blue_Z; if (png_muldiv(&xy->bluex, XYZ->blue_X, PNG_FP_1, d) == 0) return 1; if (png_muldiv(&xy->bluey, XYZ->blue_Y, PNG_FP_1, d) == 0) return 1; dwhite += d; whiteX += XYZ->blue_X; whiteY += XYZ->blue_Y; /* The reference white is simply the sum of the end-point (X,Y,Z) vectors, * thus: */ if (png_muldiv(&xy->whitex, whiteX, PNG_FP_1, dwhite) == 0) return 1; if (png_muldiv(&xy->whitey, whiteY, PNG_FP_1, dwhite) == 0) return 1; return 0; } static int png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy) { png_fixed_point red_inverse, green_inverse, blue_scale; png_fixed_point left, right, denominator; /* Check xy and, implicitly, z. Note that wide gamut color spaces typically * have end points with 0 tristimulus values (these are impossible end * points, but they are used to cover the possible colors). We check * xy->whitey against 5, not 0, to avoid a possible integer overflow. */ if (xy->redx < 0 || xy->redx > PNG_FP_1) return 1; if (xy->redy < 0 || xy->redy > PNG_FP_1-xy->redx) return 1; if (xy->greenx < 0 || xy->greenx > PNG_FP_1) return 1; if (xy->greeny < 0 || xy->greeny > PNG_FP_1-xy->greenx) return 1; if (xy->bluex < 0 || xy->bluex > PNG_FP_1) return 1; if (xy->bluey < 0 || xy->bluey > PNG_FP_1-xy->bluex) return 1; if (xy->whitex < 0 || xy->whitex > PNG_FP_1) return 1; if (xy->whitey < 5 || xy->whitey > PNG_FP_1-xy->whitex) return 1; /* The reverse calculation is more difficult because the original tristimulus * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8 * derived values were recorded in the cHRM chunk; * (red,green,blue,white)x(x,y). This loses one degree of freedom and * therefore an arbitrary ninth value has to be introduced to undo the * original transformations. * * Think of the original end-points as points in (X,Y,Z) space. The * chromaticity values (c) have the property: * * C * c = --------- * X + Y + Z * * For each c (x,y,z) from the corresponding original C (X,Y,Z). Thus the * three chromaticity values (x,y,z) for each end-point obey the * relationship: * * x + y + z = 1 * * This describes the plane in (X,Y,Z) space that intersects each axis at the * value 1.0; call this the chromaticity plane. Thus the chromaticity * calculation has scaled each end-point so that it is on the x+y+z=1 plane * and chromaticity is the intersection of the vector from the origin to the * (X,Y,Z) value with the chromaticity plane. * * To fully invert the chromaticity calculation we would need the three * end-point scale factors, (red-scale, green-scale, blue-scale), but these * were not recorded. Instead we calculated the reference white (X,Y,Z) and * recorded the chromaticity of this. The reference white (X,Y,Z) would have * given all three of the scale factors since: * * color-C = color-c * color-scale * white-C = red-C + green-C + blue-C * = red-c*red-scale + green-c*green-scale + blue-c*blue-scale * * But cHRM records only white-x and white-y, so we have lost the white scale * factor: * * white-C = white-c*white-scale * * To handle this the inverse transformation makes an arbitrary assumption * about white-scale: * * Assume: white-Y = 1.0 * Hence: white-scale = 1/white-y * Or: red-Y + green-Y + blue-Y = 1.0 * * Notice the last statement of the assumption gives an equation in three of * the nine values we want to calculate. 8 more equations come from the * above routine as summarised at the top above (the chromaticity * calculation): * * Given: color-x = color-X / (color-X + color-Y + color-Z) * Hence: (color-x - 1)*color-X + color.x*color-Y + color.x*color-Z = 0 * * This is 9 simultaneous equations in the 9 variables "color-C" and can be * solved by Cramer's rule. Cramer's rule requires calculating 10 9x9 matrix * determinants, however this is not as bad as it seems because only 28 of * the total of 90 terms in the various matrices are non-zero. Nevertheless * Cramer's rule is notoriously numerically unstable because the determinant * calculation involves the difference of large, but similar, numbers. It is * difficult to be sure that the calculation is stable for real world values * and it is certain that it becomes unstable where the end points are close * together. * * So this code uses the perhaps slightly less optimal but more * understandable and totally obvious approach of calculating color-scale. * * This algorithm depends on the precision in white-scale and that is * (1/white-y), so we can immediately see that as white-y approaches 0 the * accuracy inherent in the cHRM chunk drops off substantially. * * libpng arithmetic: a simple inversion of the above equations * ------------------------------------------------------------ * * white_scale = 1/white-y * white-X = white-x * white-scale * white-Y = 1.0 * white-Z = (1 - white-x - white-y) * white_scale * * white-C = red-C + green-C + blue-C * = red-c*red-scale + green-c*green-scale + blue-c*blue-scale * * This gives us three equations in (red-scale,green-scale,blue-scale) where * all the coefficients are now known: * * red-x*red-scale + green-x*green-scale + blue-x*blue-scale * = white-x/white-y * red-y*red-scale + green-y*green-scale + blue-y*blue-scale = 1 * red-z*red-scale + green-z*green-scale + blue-z*blue-scale * = (1 - white-x - white-y)/white-y * * In the last equation color-z is (1 - color-x - color-y) so we can add all * three equations together to get an alternative third: * * red-scale + green-scale + blue-scale = 1/white-y = white-scale * * So now we have a Cramer's rule solution where the determinants are just * 3x3 - far more tractible. Unfortunately 3x3 determinants still involve * multiplication of three coefficients so we can't guarantee to avoid * overflow in the libpng fixed point representation. Using Cramer's rule in * floating point is probably a good choice here, but it's not an option for * fixed point. Instead proceed to simplify the first two equations by * eliminating what is likely to be the largest value, blue-scale: * * blue-scale = white-scale - red-scale - green-scale * * Hence: * * (red-x - blue-x)*red-scale + (green-x - blue-x)*green-scale = * (white-x - blue-x)*white-scale * * (red-y - blue-y)*red-scale + (green-y - blue-y)*green-scale = * 1 - blue-y*white-scale * * And now we can trivially solve for (red-scale,green-scale): * * green-scale = * (white-x - blue-x)*white-scale - (red-x - blue-x)*red-scale * ----------------------------------------------------------- * green-x - blue-x * * red-scale = * 1 - blue-y*white-scale - (green-y - blue-y) * green-scale * --------------------------------------------------------- * red-y - blue-y * * Hence: * * red-scale = * ( (green-x - blue-x) * (white-y - blue-y) - * (green-y - blue-y) * (white-x - blue-x) ) / white-y * ------------------------------------------------------------------------- * (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x) * * green-scale = * ( (red-y - blue-y) * (white-x - blue-x) - * (red-x - blue-x) * (white-y - blue-y) ) / white-y * ------------------------------------------------------------------------- * (green-x - blue-x)*(red-y - blue-y)-(green-y - blue-y)*(red-x - blue-x) * * Accuracy: * The input values have 5 decimal digits of accuracy. The values are all in * the range 0 < value < 1, so simple products are in the same range but may * need up to 10 decimal digits to preserve the original precision and avoid * underflow. Because we are using a 32-bit signed representation we cannot * match this; the best is a little over 9 decimal digits, less than 10. * * The approach used here is to preserve the maximum precision within the * signed representation. Because the red-scale calculation above uses the * difference between two products of values that must be in the range -1..+1 * it is sufficient to divide the product by 7; ceil(100,000/32767*2). The * factor is irrelevant in the calculation because it is applied to both * numerator and denominator. * * Note that the values of the differences of the products of the * chromaticities in the above equations tend to be small, for example for * the sRGB chromaticities they are: * * red numerator: -0.04751 * green numerator: -0.08788 * denominator: -0.2241 (without white-y multiplication) * * The resultant Y coefficients from the chromaticities of some widely used * color space definitions are (to 15 decimal places): * * sRGB * 0.212639005871510 0.715168678767756 0.072192315360734 * Kodak ProPhoto * 0.288071128229293 0.711843217810102 0.000085653960605 * Adobe RGB * 0.297344975250536 0.627363566255466 0.075291458493998 * Adobe Wide Gamut RGB * 0.258728243040113 0.724682314948566 0.016589442011321 */ /* By the argument, above overflow should be impossible here. The return * value of 2 indicates an internal error to the caller. */ if (png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 7) == 0) return 2; if (png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 7) == 0) return 2; denominator = left - right; /* Now find the red numerator. */ if (png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 7) == 0) return 2; if (png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 7) == 0) return 2; /* Overflow is possible here and it indicates an extreme set of PNG cHRM * chunk values. This calculation actually returns the reciprocal of the * scale value because this allows us to delay the multiplication of white-y * into the denominator, which tends to produce a small number. */ if (png_muldiv(&red_inverse, xy->whitey, denominator, left-right) == 0 || red_inverse <= xy->whitey /* r+g+b scales = white scale */) return 1; /* Similarly for green_inverse: */ if (png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex, 7) == 0) return 2; if (png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 7) == 0) return 2; if (png_muldiv(&green_inverse, xy->whitey, denominator, left-right) == 0 || green_inverse <= xy->whitey) return 1; /* And the blue scale, the checks above guarantee this can't overflow but it * can still produce 0 for extreme cHRM values. */ blue_scale = png_reciprocal(xy->whitey) - png_reciprocal(red_inverse) - png_reciprocal(green_inverse); if (blue_scale <= 0) return 1; /* And fill in the png_XYZ: */ if (png_muldiv(&XYZ->red_X, xy->redx, PNG_FP_1, red_inverse) == 0) return 1; if (png_muldiv(&XYZ->red_Y, xy->redy, PNG_FP_1, red_inverse) == 0) return 1; if (png_muldiv(&XYZ->red_Z, PNG_FP_1 - xy->redx - xy->redy, PNG_FP_1, red_inverse) == 0) return 1; if (png_muldiv(&XYZ->green_X, xy->greenx, PNG_FP_1, green_inverse) == 0) return 1; if (png_muldiv(&XYZ->green_Y, xy->greeny, PNG_FP_1, green_inverse) == 0) return 1; if (png_muldiv(&XYZ->green_Z, PNG_FP_1 - xy->greenx - xy->greeny, PNG_FP_1, green_inverse) == 0) return 1; if (png_muldiv(&XYZ->blue_X, xy->bluex, blue_scale, PNG_FP_1) == 0) return 1; if (png_muldiv(&XYZ->blue_Y, xy->bluey, blue_scale, PNG_FP_1) == 0) return 1; if (png_muldiv(&XYZ->blue_Z, PNG_FP_1 - xy->bluex - xy->bluey, blue_scale, PNG_FP_1) == 0) return 1; return 0; /*success*/ } static int png_XYZ_normalize(png_XYZ *XYZ) { png_int_32 Y; if (XYZ->red_Y < 0 || XYZ->green_Y < 0 || XYZ->blue_Y < 0 || XYZ->red_X < 0 || XYZ->green_X < 0 || XYZ->blue_X < 0 || XYZ->red_Z < 0 || XYZ->green_Z < 0 || XYZ->blue_Z < 0) return 1; /* Normalize by scaling so the sum of the end-point Y values is PNG_FP_1. * IMPLEMENTATION NOTE: ANSI requires signed overflow not to occur, therefore * relying on addition of two positive values producing a negative one is not * safe. */ Y = XYZ->red_Y; if (0x7fffffff - Y < XYZ->green_X) return 1; Y += XYZ->green_Y; if (0x7fffffff - Y < XYZ->blue_X) return 1; Y += XYZ->blue_Y; if (Y != PNG_FP_1) { if (png_muldiv(&XYZ->red_X, XYZ->red_X, PNG_FP_1, Y) == 0) return 1; if (png_muldiv(&XYZ->red_Y, XYZ->red_Y, PNG_FP_1, Y) == 0) return 1; if (png_muldiv(&XYZ->red_Z, XYZ->red_Z, PNG_FP_1, Y) == 0) return 1; if (png_muldiv(&XYZ->green_X, XYZ->green_X, PNG_FP_1, Y) == 0) return 1; if (png_muldiv(&XYZ->green_Y, XYZ->green_Y, PNG_FP_1, Y) == 0) return 1; if (png_muldiv(&XYZ->green_Z, XYZ->green_Z, PNG_FP_1, Y) == 0) return 1; if (png_muldiv(&XYZ->blue_X, XYZ->blue_X, PNG_FP_1, Y) == 0) return 1; if (png_muldiv(&XYZ->blue_Y, XYZ->blue_Y, PNG_FP_1, Y) == 0) return 1; if (png_muldiv(&XYZ->blue_Z, XYZ->blue_Z, PNG_FP_1, Y) == 0) return 1; } return 0; } static int png_colorspace_endpoints_match(const png_xy *xy1, const png_xy *xy2, int delta) { /* Allow an error of +/-0.01 (absolute value) on each chromaticity */ if (PNG_OUT_OF_RANGE(xy1->whitex, xy2->whitex,delta) || PNG_OUT_OF_RANGE(xy1->whitey, xy2->whitey,delta) || PNG_OUT_OF_RANGE(xy1->redx, xy2->redx, delta) || PNG_OUT_OF_RANGE(xy1->redy, xy2->redy, delta) || PNG_OUT_OF_RANGE(xy1->greenx, xy2->greenx,delta) || PNG_OUT_OF_RANGE(xy1->greeny, xy2->greeny,delta) || PNG_OUT_OF_RANGE(xy1->bluex, xy2->bluex, delta) || PNG_OUT_OF_RANGE(xy1->bluey, xy2->bluey, delta)) return 0; return 1; } /* Added in libpng-1.6.0, a different check for the validity of a set of cHRM * chunk chromaticities. Earlier checks used to simply look for the overflow * condition (where the determinant of the matrix to solve for XYZ ends up zero * because the chromaticity values are not all distinct.) Despite this it is * theoretically possible to produce chromaticities that are apparently valid * but that rapidly degrade to invalid, potentially crashing, sets because of * arithmetic inaccuracies when calculations are performed on them. The new * check is to round-trip xy -> XYZ -> xy and then check that the result is * within a small percentage of the original. */ static int png_colorspace_check_xy(png_XYZ *XYZ, const png_xy *xy) { int result; png_xy xy_test; /* As a side-effect this routine also returns the XYZ endpoints. */ result = png_XYZ_from_xy(XYZ, xy); if (result != 0) return result; result = png_xy_from_XYZ(&xy_test, XYZ); if (result != 0) return result; if (png_colorspace_endpoints_match(xy, &xy_test, 5/*actually, the math is pretty accurate*/) != 0) return 0; /* Too much slip */ return 1; } /* This is the check going the other way. The XYZ is modified to normalize it * (another side-effect) and the xy chromaticities are returned. */ static int png_colorspace_check_XYZ(png_xy *xy, png_XYZ *XYZ) { int result; png_XYZ XYZtemp; result = png_XYZ_normalize(XYZ); if (result != 0) return result; result = png_xy_from_XYZ(xy, XYZ); if (result != 0) return result; XYZtemp = *XYZ; return png_colorspace_check_xy(&XYZtemp, xy); } /* Used to check for an endpoint match against sRGB */ static const png_xy sRGB_xy = /* From ITU-R BT.709-3 */ { /* color x y */ /* red */ 64000, 33000, /* green */ 30000, 60000, /* blue */ 15000, 6000, /* white */ 31270, 32900 }; static int png_colorspace_set_xy_and_XYZ(png_const_structrp png_ptr, png_colorspacerp colorspace, const png_xy *xy, const png_XYZ *XYZ, int preferred) { if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0) return 0; /* The consistency check is performed on the chromaticities; this factors out * variations because of the normalization (or not) of the end point Y * values. */ if (preferred < 2 && (colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0) { /* The end points must be reasonably close to any we already have. The * following allows an error of up to +/-.001 */ if (png_colorspace_endpoints_match(xy, &colorspace->end_points_xy, 100) == 0) { colorspace->flags |= PNG_COLORSPACE_INVALID; png_benign_error(png_ptr, "inconsistent chromaticities"); return 0; /* failed */ } /* Only overwrite with preferred values */ if (preferred == 0) return 1; /* ok, but no change */ } colorspace->end_points_xy = *xy; colorspace->end_points_XYZ = *XYZ; colorspace->flags |= PNG_COLORSPACE_HAVE_ENDPOINTS; /* The end points are normally quoted to two decimal digits, so allow +/-0.01 * on this test. */ if (png_colorspace_endpoints_match(xy, &sRGB_xy, 1000) != 0) colorspace->flags |= PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB; else colorspace->flags &= PNG_COLORSPACE_CANCEL( PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB); return 2; /* ok and changed */ } int /* PRIVATE */ png_colorspace_set_chromaticities(png_const_structrp png_ptr, png_colorspacerp colorspace, const png_xy *xy, int preferred) { /* We must check the end points to ensure they are reasonable - in the past * color management systems have crashed as a result of getting bogus * colorant values, while this isn't the fault of libpng it is the * responsibility of libpng because PNG carries the bomb and libpng is in a * position to protect against it. */ png_XYZ XYZ; switch (png_colorspace_check_xy(&XYZ, xy)) { case 0: /* success */ return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, xy, &XYZ, preferred); case 1: /* We can't invert the chromaticities so we can't produce value XYZ * values. Likely as not a color management system will fail too. */ colorspace->flags |= PNG_COLORSPACE_INVALID; png_benign_error(png_ptr, "invalid chromaticities"); break; default: /* libpng is broken; this should be a warning but if it happens we * want error reports so for the moment it is an error. */ colorspace->flags |= PNG_COLORSPACE_INVALID; png_error(png_ptr, "internal error checking chromaticities"); } return 0; /* failed */ } int /* PRIVATE */ png_colorspace_set_endpoints(png_const_structrp png_ptr, png_colorspacerp colorspace, const png_XYZ *XYZ_in, int preferred) { png_XYZ XYZ = *XYZ_in; png_xy xy; switch (png_colorspace_check_XYZ(&xy, &XYZ)) { case 0: return png_colorspace_set_xy_and_XYZ(png_ptr, colorspace, &xy, &XYZ, preferred); case 1: /* End points are invalid. */ colorspace->flags |= PNG_COLORSPACE_INVALID; png_benign_error(png_ptr, "invalid end points"); break; default: colorspace->flags |= PNG_COLORSPACE_INVALID; png_error(png_ptr, "internal error checking chromaticities"); } return 0; /* failed */ } #if defined(PNG_sRGB_SUPPORTED) || defined(PNG_iCCP_SUPPORTED) /* Error message generation */ static char png_icc_tag_char(png_uint_32 byte) { byte &= 0xff; if (byte >= 32 && byte <= 126) return (char)byte; else return '?'; } static void png_icc_tag_name(char *name, png_uint_32 tag) { name[0] = '\''; name[1] = png_icc_tag_char(tag >> 24); name[2] = png_icc_tag_char(tag >> 16); name[3] = png_icc_tag_char(tag >> 8); name[4] = png_icc_tag_char(tag ); name[5] = '\''; } static int is_ICC_signature_char(png_alloc_size_t it) { return it == 32 || (it >= 48 && it <= 57) || (it >= 65 && it <= 90) || (it >= 97 && it <= 122); } static int is_ICC_signature(png_alloc_size_t it) { return is_ICC_signature_char(it >> 24) /* checks all the top bits */ && is_ICC_signature_char((it >> 16) & 0xff) && is_ICC_signature_char((it >> 8) & 0xff) && is_ICC_signature_char(it & 0xff); } static int png_icc_profile_error(png_const_structrp png_ptr, png_colorspacerp colorspace, png_const_charp name, png_alloc_size_t value, png_const_charp reason) { size_t pos; char message[196]; /* see below for calculation */ if (colorspace != NULL) colorspace->flags |= PNG_COLORSPACE_INVALID; pos = png_safecat(message, (sizeof message), 0, "profile '"); /* 9 chars */ pos = png_safecat(message, pos+79, pos, name); /* Truncate to 79 chars */ pos = png_safecat(message, (sizeof message), pos, "': "); /* +2 = 90 */ if (is_ICC_signature(value) != 0) { /* So 'value' is at most 4 bytes and the following cast is safe */ png_icc_tag_name(message+pos, (png_uint_32)value); pos += 6; /* total +8; less than the else clause */ message[pos++] = ':'; message[pos++] = ' '; } # ifdef PNG_WARNINGS_SUPPORTED else { char number[PNG_NUMBER_BUFFER_SIZE]; /* +24 = 114*/ pos = png_safecat(message, (sizeof message), pos, png_format_number(number, number+(sizeof number), PNG_NUMBER_FORMAT_x, value)); pos = png_safecat(message, (sizeof message), pos, "h: "); /*+2 = 116*/ } # endif /* The 'reason' is an arbitrary message, allow +79 maximum 195 */ pos = png_safecat(message, (sizeof message), pos, reason); PNG_UNUSED(pos) /* This is recoverable, but make it unconditionally an app_error on write to * avoid writing invalid ICC profiles into PNG files (i.e., we handle them * on read, with a warning, but on write unless the app turns off * application errors the PNG won't be written.) */ png_chunk_report(png_ptr, message, (colorspace != NULL) ? PNG_CHUNK_ERROR : PNG_CHUNK_WRITE_ERROR); return 0; } #endif /* sRGB || iCCP */ #ifdef PNG_sRGB_SUPPORTED int /* PRIVATE */ png_colorspace_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace, int intent) { /* sRGB sets known gamma, end points and (from the chunk) intent. */ /* IMPORTANT: these are not necessarily the values found in an ICC profile * because ICC profiles store values adapted to a D50 environment; it is * expected that the ICC profile mediaWhitePointTag will be D50; see the * checks and code elsewhere to understand this better. * * These XYZ values, which are accurate to 5dp, produce rgb to gray * coefficients of (6968,23435,2366), which are reduced (because they add up * to 32769 not 32768) to (6968,23434,2366). These are the values that * libpng has traditionally used (and are the best values given the 15bit * algorithm used by the rgb to gray code.) */ static const png_XYZ sRGB_XYZ = /* D65 XYZ (*not* the D50 adapted values!) */ { /* color X Y Z */ /* red */ 41239, 21264, 1933, /* green */ 35758, 71517, 11919, /* blue */ 18048, 7219, 95053 }; /* Do nothing if the colorspace is already invalidated. */ if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0) return 0; /* Check the intent, then check for existing settings. It is valid for the * PNG file to have cHRM or gAMA chunks along with sRGB, but the values must * be consistent with the correct values. If, however, this function is * called below because an iCCP chunk matches sRGB then it is quite * conceivable that an older app recorded incorrect gAMA and cHRM because of * an incorrect calculation based on the values in the profile - this does * *not* invalidate the profile (though it still produces an error, which can * be ignored.) */ if (intent < 0 || intent >= PNG_sRGB_INTENT_LAST) return png_icc_profile_error(png_ptr, colorspace, "sRGB", (png_alloc_size_t)intent, "invalid sRGB rendering intent"); if ((colorspace->flags & PNG_COLORSPACE_HAVE_INTENT) != 0 && colorspace->rendering_intent != intent) return png_icc_profile_error(png_ptr, colorspace, "sRGB", (png_alloc_size_t)intent, "inconsistent rendering intents"); if ((colorspace->flags & PNG_COLORSPACE_FROM_sRGB) != 0) { png_benign_error(png_ptr, "duplicate sRGB information ignored"); return 0; } /* If the standard sRGB cHRM chunk does not match the one from the PNG file * warn but overwrite the value with the correct one. */ if ((colorspace->flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0 && !png_colorspace_endpoints_match(&sRGB_xy, &colorspace->end_points_xy, 100)) png_chunk_report(png_ptr, "cHRM chunk does not match sRGB", PNG_CHUNK_ERROR); /* This check is just done for the error reporting - the routine always * returns true when the 'from' argument corresponds to sRGB (2). */ (void)png_colorspace_check_gamma(png_ptr, colorspace, PNG_GAMMA_sRGB_INVERSE, 2/*from sRGB*/); /* intent: bugs in GCC force 'int' to be used as the parameter type. */ colorspace->rendering_intent = (png_uint_16)intent; colorspace->flags |= PNG_COLORSPACE_HAVE_INTENT; /* endpoints */ colorspace->end_points_xy = sRGB_xy; colorspace->end_points_XYZ = sRGB_XYZ; colorspace->flags |= (PNG_COLORSPACE_HAVE_ENDPOINTS|PNG_COLORSPACE_ENDPOINTS_MATCH_sRGB); /* gamma */ colorspace->gamma = PNG_GAMMA_sRGB_INVERSE; colorspace->flags |= PNG_COLORSPACE_HAVE_GAMMA; /* Finally record that we have an sRGB profile */ colorspace->flags |= (PNG_COLORSPACE_MATCHES_sRGB|PNG_COLORSPACE_FROM_sRGB); return 1; /* set */ } #endif /* sRGB */ #ifdef PNG_iCCP_SUPPORTED /* Encoded value of D50 as an ICC XYZNumber. From the ICC 2010 spec the value * is XYZ(0.9642,1.0,0.8249), which scales to: * * (63189.8112, 65536, 54060.6464) */ static const png_byte D50_nCIEXYZ[12] = { 0x00, 0x00, 0xf6, 0xd6, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0xd3, 0x2d }; static int /* bool */ icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace, png_const_charp name, png_uint_32 profile_length) { if (profile_length < 132) return png_icc_profile_error(png_ptr, colorspace, name, profile_length, "too short"); return 1; } #ifdef PNG_READ_iCCP_SUPPORTED int /* PRIVATE */ png_icc_check_length(png_const_structrp png_ptr, png_colorspacerp colorspace, png_const_charp name, png_uint_32 profile_length) { if (!icc_check_length(png_ptr, colorspace, name, profile_length)) return 0; /* This needs to be here because the 'normal' check is in * png_decompress_chunk, yet this happens after the attempt to * png_malloc_base the required data. We only need this on read; on write * the caller supplies the profile buffer so libpng doesn't allocate it. See * the call to icc_check_length below (the write case). */ # ifdef PNG_SET_USER_LIMITS_SUPPORTED else if (png_ptr->user_chunk_malloc_max > 0 && png_ptr->user_chunk_malloc_max < profile_length) return png_icc_profile_error(png_ptr, colorspace, name, profile_length, "exceeds application limits"); # elif PNG_USER_CHUNK_MALLOC_MAX > 0 else if (PNG_USER_CHUNK_MALLOC_MAX < profile_length) return png_icc_profile_error(png_ptr, colorspace, name, profile_length, "exceeds libpng limits"); # else /* !SET_USER_LIMITS */ /* This will get compiled out on all 32-bit and better systems. */ else if (PNG_SIZE_MAX < profile_length) return png_icc_profile_error(png_ptr, colorspace, name, profile_length, "exceeds system limits"); # endif /* !SET_USER_LIMITS */ return 1; } #endif /* READ_iCCP */ int /* PRIVATE */ png_icc_check_header(png_const_structrp png_ptr, png_colorspacerp colorspace, png_const_charp name, png_uint_32 profile_length, png_const_bytep profile/* first 132 bytes only */, int color_type) { png_uint_32 temp; /* Length check; this cannot be ignored in this code because profile_length * is used later to check the tag table, so even if the profile seems over * long profile_length from the caller must be correct. The caller can fix * this up on read or write by just passing in the profile header length. */ temp = png_get_uint_32(profile); if (temp != profile_length) return png_icc_profile_error(png_ptr, colorspace, name, temp, "length does not match profile"); temp = (png_uint_32) (*(profile+8)); if (temp > 3 && (profile_length & 3)) return png_icc_profile_error(png_ptr, colorspace, name, profile_length, "invalid length"); temp = png_get_uint_32(profile+128); /* tag count: 12 bytes/tag */ if (temp > 357913930 || /* (2^32-4-132)/12: maximum possible tag count */ profile_length < 132+12*temp) /* truncated tag table */ return png_icc_profile_error(png_ptr, colorspace, name, temp, "tag count too large"); /* The 'intent' must be valid or we can't store it, ICC limits the intent to * 16 bits. */ temp = png_get_uint_32(profile+64); if (temp >= 0xffff) /* The ICC limit */ return png_icc_profile_error(png_ptr, colorspace, name, temp, "invalid rendering intent"); /* This is just a warning because the profile may be valid in future * versions. */ if (temp >= PNG_sRGB_INTENT_LAST) (void)png_icc_profile_error(png_ptr, NULL, name, temp, "intent outside defined range"); /* At this point the tag table can't be checked because it hasn't necessarily * been loaded; however, various header fields can be checked. These checks * are for values permitted by the PNG spec in an ICC profile; the PNG spec * restricts the profiles that can be passed in an iCCP chunk (they must be * appropriate to processing PNG data!) */ /* Data checks (could be skipped). These checks must be independent of the * version number; however, the version number doesn't accommodate changes in * the header fields (just the known tags and the interpretation of the * data.) */ temp = png_get_uint_32(profile+36); /* signature 'ascp' */ if (temp != 0x61637370) return png_icc_profile_error(png_ptr, colorspace, name, temp, "invalid signature"); /* Currently the PCS illuminant/adopted white point (the computational * white point) are required to be D50, * however the profile contains a record of the illuminant so perhaps ICC * expects to be able to change this in the future (despite the rationale in * the introduction for using a fixed PCS adopted white.) Consequently the * following is just a warning. */ if (memcmp(profile+68, D50_nCIEXYZ, 12) != 0) (void)png_icc_profile_error(png_ptr, NULL, name, 0/*no tag value*/, "PCS illuminant is not D50"); /* The PNG spec requires this: * "If the iCCP chunk is present, the image samples conform to the colour * space represented by the embedded ICC profile as defined by the * International Color Consortium [ICC]. The colour space of the ICC profile * shall be an RGB colour space for colour images (PNG colour types 2, 3, and * 6), or a greyscale colour space for greyscale images (PNG colour types 0 * and 4)." * * This checking code ensures the embedded profile (on either read or write) * conforms to the specification requirements. Notice that an ICC 'gray' * color-space profile contains the information to transform the monochrome * data to XYZ or L*a*b (according to which PCS the profile uses) and this * should be used in preference to the standard libpng K channel replication * into R, G and B channels. * * Previously it was suggested that an RGB profile on grayscale data could be * handled. However it it is clear that using an RGB profile in this context * must be an error - there is no specification of what it means. Thus it is * almost certainly more correct to ignore the profile. */ temp = png_get_uint_32(profile+16); /* data colour space field */ switch (temp) { case 0x52474220: /* 'RGB ' */ if ((color_type & PNG_COLOR_MASK_COLOR) == 0) return png_icc_profile_error(png_ptr, colorspace, name, temp, "RGB color space not permitted on grayscale PNG"); break; case 0x47524159: /* 'GRAY' */ if ((color_type & PNG_COLOR_MASK_COLOR) != 0) return png_icc_profile_error(png_ptr, colorspace, name, temp, "Gray color space not permitted on RGB PNG"); break; default: return png_icc_profile_error(png_ptr, colorspace, name, temp, "invalid ICC profile color space"); } /* It is up to the application to check that the profile class matches the * application requirements; the spec provides no guidance, but it's pretty * weird if the profile is not scanner ('scnr'), monitor ('mntr'), printer * ('prtr') or 'spac' (for generic color spaces). Issue a warning in these * cases. Issue an error for device link or abstract profiles - these don't * contain the records necessary to transform the color-space to anything * other than the target device (and not even that for an abstract profile). * Profiles of these classes may not be embedded in images. */ temp = png_get_uint_32(profile+12); /* profile/device class */ switch (temp) { case 0x73636e72: /* 'scnr' */ case 0x6d6e7472: /* 'mntr' */ case 0x70727472: /* 'prtr' */ case 0x73706163: /* 'spac' */ /* All supported */ break; case 0x61627374: /* 'abst' */ /* May not be embedded in an image */ return png_icc_profile_error(png_ptr, colorspace, name, temp, "invalid embedded Abstract ICC profile"); case 0x6c696e6b: /* 'link' */ /* DeviceLink profiles cannot be interpreted in a non-device specific * fashion, if an app uses the AToB0Tag in the profile the results are * undefined unless the result is sent to the intended device, * therefore a DeviceLink profile should not be found embedded in a * PNG. */ return png_icc_profile_error(png_ptr, colorspace, name, temp, "unexpected DeviceLink ICC profile class"); case 0x6e6d636c: /* 'nmcl' */ /* A NamedColor profile is also device specific, however it doesn't * contain an AToB0 tag that is open to misinterpretation. Almost * certainly it will fail the tests below. */ (void)png_icc_profile_error(png_ptr, NULL, name, temp, "unexpected NamedColor ICC profile class"); break; default: /* To allow for future enhancements to the profile accept unrecognized * profile classes with a warning, these then hit the test below on the * tag content to ensure they are backward compatible with one of the * understood profiles. */ (void)png_icc_profile_error(png_ptr, NULL, name, temp, "unrecognized ICC profile class"); break; } /* For any profile other than a device link one the PCS must be encoded * either in XYZ or Lab. */ temp = png_get_uint_32(profile+20); switch (temp) { case 0x58595a20: /* 'XYZ ' */ case 0x4c616220: /* 'Lab ' */ break; default: return png_icc_profile_error(png_ptr, colorspace, name, temp, "unexpected ICC PCS encoding"); } return 1; } int /* PRIVATE */ png_icc_check_tag_table(png_const_structrp png_ptr, png_colorspacerp colorspace, png_const_charp name, png_uint_32 profile_length, png_const_bytep profile /* header plus whole tag table */) { png_uint_32 tag_count = png_get_uint_32(profile+128); png_uint_32 itag; png_const_bytep tag = profile+132; /* The first tag */ /* First scan all the tags in the table and add bits to the icc_info value * (temporarily in 'tags'). */ for (itag=0; itag < tag_count; ++itag, tag += 12) { png_uint_32 tag_id = png_get_uint_32(tag+0); png_uint_32 tag_start = png_get_uint_32(tag+4); /* must be aligned */ png_uint_32 tag_length = png_get_uint_32(tag+8);/* not padded */ /* The ICC specification does not exclude zero length tags, therefore the * start might actually be anywhere if there is no data, but this would be * a clear abuse of the intent of the standard so the start is checked for * being in range. All defined tag types have an 8 byte header - a 4 byte * type signature then 0. */ /* This is a hard error; potentially it can cause read outside the * profile. */ if (tag_start > profile_length || tag_length > profile_length - tag_start) return png_icc_profile_error(png_ptr, colorspace, name, tag_id, "ICC profile tag outside profile"); if ((tag_start & 3) != 0) { /* CNHP730S.icc shipped with Microsoft Windows 64 violates this; it is * only a warning here because libpng does not care about the * alignment. */ (void)png_icc_profile_error(png_ptr, NULL, name, tag_id, "ICC profile tag start not a multiple of 4"); } } return 1; /* success, maybe with warnings */ } #ifdef PNG_sRGB_SUPPORTED #if PNG_sRGB_PROFILE_CHECKS >= 0 /* Information about the known ICC sRGB profiles */ static const struct { png_uint_32 adler, crc, length; png_uint_32 md5[4]; png_byte have_md5; png_byte is_broken; png_uint_16 intent; # define PNG_MD5(a,b,c,d) { a, b, c, d }, (a!=0)||(b!=0)||(c!=0)||(d!=0) # define PNG_ICC_CHECKSUM(adler, crc, md5, intent, broke, date, length, fname)\ { adler, crc, length, md5, broke, intent }, } png_sRGB_checks[] = { /* This data comes from contrib/tools/checksum-icc run on downloads of * all four ICC sRGB profiles from www.color.org. */ /* adler32, crc32, MD5[4], intent, date, length, file-name */ PNG_ICC_CHECKSUM(0x0a3fd9f6, 0x3b8772b9, PNG_MD5(0x29f83dde, 0xaff255ae, 0x7842fae4, 0xca83390d), 0, 0, "2009/03/27 21:36:31", 3048, "sRGB_IEC61966-2-1_black_scaled.icc") /* ICC sRGB v2 perceptual no black-compensation: */ PNG_ICC_CHECKSUM(0x4909e5e1, 0x427ebb21, PNG_MD5(0xc95bd637, 0xe95d8a3b, 0x0df38f99, 0xc1320389), 1, 0, "2009/03/27 21:37:45", 3052, "sRGB_IEC61966-2-1_no_black_scaling.icc") PNG_ICC_CHECKSUM(0xfd2144a1, 0x306fd8ae, PNG_MD5(0xfc663378, 0x37e2886b, 0xfd72e983, 0x8228f1b8), 0, 0, "2009/08/10 17:28:01", 60988, "sRGB_v4_ICC_preference_displayclass.icc") /* ICC sRGB v4 perceptual */ PNG_ICC_CHECKSUM(0x209c35d2, 0xbbef7812, PNG_MD5(0x34562abf, 0x994ccd06, 0x6d2c5721, 0xd0d68c5d), 0, 0, "2007/07/25 00:05:37", 60960, "sRGB_v4_ICC_preference.icc") /* The following profiles have no known MD5 checksum. If there is a match * on the (empty) MD5 the other fields are used to attempt a match and * a warning is produced. The first two of these profiles have a 'cprt' tag * which suggests that they were also made by Hewlett Packard. */ PNG_ICC_CHECKSUM(0xa054d762, 0x5d5129ce, PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 0, "2004/07/21 18:57:42", 3024, "sRGB_IEC61966-2-1_noBPC.icc") /* This is a 'mntr' (display) profile with a mediaWhitePointTag that does not * match the D50 PCS illuminant in the header (it is in fact the D65 values, * so the white point is recorded as the un-adapted value.) The profiles * below only differ in one byte - the intent - and are basically the same as * the previous profile except for the mediaWhitePointTag error and a missing * chromaticAdaptationTag. */ PNG_ICC_CHECKSUM(0xf784f3fb, 0x182ea552, PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 0, 1/*broken*/, "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 perceptual") PNG_ICC_CHECKSUM(0x0398f3fc, 0xf29e526d, PNG_MD5(0x00000000, 0x00000000, 0x00000000, 0x00000000), 1, 1/*broken*/, "1998/02/09 06:49:00", 3144, "HP-Microsoft sRGB v2 media-relative") }; static int png_compare_ICC_profile_with_sRGB(png_const_structrp png_ptr, png_const_bytep profile, uLong adler) { /* The quick check is to verify just the MD5 signature and trust the * rest of the data. Because the profile has already been verified for * correctness this is safe. png_colorspace_set_sRGB will check the 'intent' * field too, so if the profile has been edited with an intent not defined * by sRGB (but maybe defined by a later ICC specification) the read of * the profile will fail at that point. */ png_uint_32 length = 0; png_uint_32 intent = 0x10000; /* invalid */ #if PNG_sRGB_PROFILE_CHECKS > 1 uLong crc = 0; /* the value for 0 length data */ #endif unsigned int i; #ifdef PNG_SET_OPTION_SUPPORTED /* First see if PNG_SKIP_sRGB_CHECK_PROFILE has been set to "on" */ if (((png_ptr->options >> PNG_SKIP_sRGB_CHECK_PROFILE) & 3) == PNG_OPTION_ON) return 0; #endif for (i=0; i < (sizeof png_sRGB_checks) / (sizeof png_sRGB_checks[0]); ++i) { if (png_get_uint_32(profile+84) == png_sRGB_checks[i].md5[0] && png_get_uint_32(profile+88) == png_sRGB_checks[i].md5[1] && png_get_uint_32(profile+92) == png_sRGB_checks[i].md5[2] && png_get_uint_32(profile+96) == png_sRGB_checks[i].md5[3]) { /* This may be one of the old HP profiles without an MD5, in that * case we can only use the length and Adler32 (note that these * are not used by default if there is an MD5!) */ # if PNG_sRGB_PROFILE_CHECKS == 0 if (png_sRGB_checks[i].have_md5 != 0) return 1+png_sRGB_checks[i].is_broken; # endif /* Profile is unsigned or more checks have been configured in. */ if (length == 0) { length = png_get_uint_32(profile); intent = png_get_uint_32(profile+64); } /* Length *and* intent must match */ if (length == (png_uint_32) png_sRGB_checks[i].length && intent == (png_uint_32) png_sRGB_checks[i].intent) { /* Now calculate the adler32 if not done already. */ if (adler == 0) { adler = adler32(0, NULL, 0); adler = adler32(adler, profile, length); } if (adler == png_sRGB_checks[i].adler) { /* These basic checks suggest that the data has not been * modified, but if the check level is more than 1 perform * our own crc32 checksum on the data. */ # if PNG_sRGB_PROFILE_CHECKS > 1 if (crc == 0) { crc = crc32(0, NULL, 0); crc = crc32(crc, profile, length); } /* So this check must pass for the 'return' below to happen. */ if (crc == png_sRGB_checks[i].crc) # endif { if (png_sRGB_checks[i].is_broken != 0) { /* These profiles are known to have bad data that may cause * problems if they are used, therefore attempt to * discourage their use, skip the 'have_md5' warning below, * which is made irrelevant by this error. */ png_chunk_report(png_ptr, "known incorrect sRGB profile", PNG_CHUNK_ERROR); } /* Warn that this being done; this isn't even an error since * the profile is perfectly valid, but it would be nice if * people used the up-to-date ones. */ else if (png_sRGB_checks[i].have_md5 == 0) { png_chunk_report(png_ptr, "out-of-date sRGB profile with no signature", PNG_CHUNK_WARNING); } return 1+png_sRGB_checks[i].is_broken; } } # if PNG_sRGB_PROFILE_CHECKS > 0 /* The signature matched, but the profile had been changed in some * way. This probably indicates a data error or uninformed hacking. * Fall through to "no match". */ png_chunk_report(png_ptr, "Not recognizing known sRGB profile that has been edited", PNG_CHUNK_WARNING); break; # endif } } } return 0; /* no match */ } void /* PRIVATE */ png_icc_set_sRGB(png_const_structrp png_ptr, png_colorspacerp colorspace, png_const_bytep profile, uLong adler) { /* Is this profile one of the known ICC sRGB profiles? If it is, just set * the sRGB information. */ if (png_compare_ICC_profile_with_sRGB(png_ptr, profile, adler) != 0) (void)png_colorspace_set_sRGB(png_ptr, colorspace, (int)/*already checked*/png_get_uint_32(profile+64)); } #endif /* PNG_sRGB_PROFILE_CHECKS >= 0 */ #endif /* sRGB */ int /* PRIVATE */ png_colorspace_set_ICC(png_const_structrp png_ptr, png_colorspacerp colorspace, png_const_charp name, png_uint_32 profile_length, png_const_bytep profile, int color_type) { if ((colorspace->flags & PNG_COLORSPACE_INVALID) != 0) return 0; if (icc_check_length(png_ptr, colorspace, name, profile_length) != 0 && png_icc_check_header(png_ptr, colorspace, name, profile_length, profile, color_type) != 0 && png_icc_check_tag_table(png_ptr, colorspace, name, profile_length, profile) != 0) { # if defined(PNG_sRGB_SUPPORTED) && PNG_sRGB_PROFILE_CHECKS >= 0 /* If no sRGB support, don't try storing sRGB information */ png_icc_set_sRGB(png_ptr, colorspace, profile, 0); # endif return 1; } /* Failure case */ return 0; } #endif /* iCCP */ #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED void /* PRIVATE */ png_colorspace_set_rgb_coefficients(png_structrp png_ptr) { /* Set the rgb_to_gray coefficients from the colorspace. */ if (png_ptr->rgb_to_gray_coefficients_set == 0 && (png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_ENDPOINTS) != 0) { /* png_set_background has not been called, get the coefficients from the Y * values of the colorspace colorants. */ png_fixed_point r = png_ptr->colorspace.end_points_XYZ.red_Y; png_fixed_point g = png_ptr->colorspace.end_points_XYZ.green_Y; png_fixed_point b = png_ptr->colorspace.end_points_XYZ.blue_Y; png_fixed_point total = r+g+b; if (total > 0 && r >= 0 && png_muldiv(&r, r, 32768, total) && r >= 0 && r <= 32768 && g >= 0 && png_muldiv(&g, g, 32768, total) && g >= 0 && g <= 32768 && b >= 0 && png_muldiv(&b, b, 32768, total) && b >= 0 && b <= 32768 && r+g+b <= 32769) { /* We allow 0 coefficients here. r+g+b may be 32769 if two or * all of the coefficients were rounded up. Handle this by * reducing the *largest* coefficient by 1; this matches the * approach used for the default coefficients in pngrtran.c */ int add = 0; if (r+g+b > 32768) add = -1; else if (r+g+b < 32768) add = 1; if (add != 0) { if (g >= r && g >= b) g += add; else if (r >= g && r >= b) r += add; else b += add; } /* Check for an internal error. */ if (r+g+b != 32768) png_error(png_ptr, "internal error handling cHRM coefficients"); else { png_ptr->rgb_to_gray_red_coeff = (png_uint_16)r; png_ptr->rgb_to_gray_green_coeff = (png_uint_16)g; } } /* This is a png_error at present even though it could be ignored - * it should never happen, but it is important that if it does, the * bug is fixed. */ else png_error(png_ptr, "internal error handling cHRM->XYZ"); } } #endif /* READ_RGB_TO_GRAY */ #endif /* COLORSPACE */ #ifdef __GNUC__ /* This exists solely to work round a warning from GNU C. */ static int /* PRIVATE */ png_gt(size_t a, size_t b) { return a > b; } #else # define png_gt(a,b) ((a) > (b)) #endif void /* PRIVATE */ png_check_IHDR(png_const_structrp png_ptr, png_uint_32 width, png_uint_32 height, int bit_depth, int color_type, int interlace_type, int compression_type, int filter_type) { int error = 0; /* Check for width and height valid values */ if (width == 0) { png_warning(png_ptr, "Image width is zero in IHDR"); error = 1; } if (width > PNG_UINT_31_MAX) { png_warning(png_ptr, "Invalid image width in IHDR"); error = 1; } if (png_gt(((width + 7) & (~7U)), ((PNG_SIZE_MAX - 48 /* big_row_buf hack */ - 1) /* filter byte */ / 8) /* 8-byte RGBA pixels */ - 1)) /* extra max_pixel_depth pad */ { /* The size of the row must be within the limits of this architecture. * Because the read code can perform arbitrary transformations the * maximum size is checked here. Because the code in png_read_start_row * adds extra space "for safety's sake" in several places a conservative * limit is used here. * * NOTE: it would be far better to check the size that is actually used, * but the effect in the real world is minor and the changes are more * extensive, therefore much more dangerous and much more difficult to * write in a way that avoids compiler warnings. */ png_warning(png_ptr, "Image width is too large for this architecture"); error = 1; } #ifdef PNG_SET_USER_LIMITS_SUPPORTED if (width > png_ptr->user_width_max) #else if (width > PNG_USER_WIDTH_MAX) #endif { png_warning(png_ptr, "Image width exceeds user limit in IHDR"); error = 1; } if (height == 0) { png_warning(png_ptr, "Image height is zero in IHDR"); error = 1; } if (height > PNG_UINT_31_MAX) { png_warning(png_ptr, "Invalid image height in IHDR"); error = 1; } #ifdef PNG_SET_USER_LIMITS_SUPPORTED if (height > png_ptr->user_height_max) #else if (height > PNG_USER_HEIGHT_MAX) #endif { png_warning(png_ptr, "Image height exceeds user limit in IHDR"); error = 1; } /* Check other values */ if (bit_depth != 1 && bit_depth != 2 && bit_depth != 4 && bit_depth != 8 && bit_depth != 16) { png_warning(png_ptr, "Invalid bit depth in IHDR"); error = 1; } if (color_type < 0 || color_type == 1 || color_type == 5 || color_type > 6) { png_warning(png_ptr, "Invalid color type in IHDR"); error = 1; } if (((color_type == PNG_COLOR_TYPE_PALETTE) && bit_depth > 8) || ((color_type == PNG_COLOR_TYPE_RGB || color_type == PNG_COLOR_TYPE_GRAY_ALPHA || color_type == PNG_COLOR_TYPE_RGB_ALPHA) && bit_depth < 8)) { png_warning(png_ptr, "Invalid color type/bit depth combination in IHDR"); error = 1; } if (interlace_type >= PNG_INTERLACE_LAST) { png_warning(png_ptr, "Unknown interlace method in IHDR"); error = 1; } if (compression_type != PNG_COMPRESSION_TYPE_BASE) { png_warning(png_ptr, "Unknown compression method in IHDR"); error = 1; } #ifdef PNG_MNG_FEATURES_SUPPORTED /* Accept filter_method 64 (intrapixel differencing) only if * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and * 2. Libpng did not read a PNG signature (this filter_method is only * used in PNG datastreams that are embedded in MNG datastreams) and * 3. The application called png_permit_mng_features with a mask that * included PNG_FLAG_MNG_FILTER_64 and * 4. The filter_method is 64 and * 5. The color_type is RGB or RGBA */ if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 && png_ptr->mng_features_permitted != 0) png_warning(png_ptr, "MNG features are not allowed in a PNG datastream"); if (filter_type != PNG_FILTER_TYPE_BASE) { if (!((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) != 0 && (filter_type == PNG_INTRAPIXEL_DIFFERENCING) && ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) == 0) && (color_type == PNG_COLOR_TYPE_RGB || color_type == PNG_COLOR_TYPE_RGB_ALPHA))) { png_warning(png_ptr, "Unknown filter method in IHDR"); error = 1; } if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0) { png_warning(png_ptr, "Invalid filter method in IHDR"); error = 1; } } #else if (filter_type != PNG_FILTER_TYPE_BASE) { png_warning(png_ptr, "Unknown filter method in IHDR"); error = 1; } #endif if (error == 1) png_error(png_ptr, "Invalid IHDR data"); } #if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED) /* ASCII to fp functions */ /* Check an ASCII formatted floating point value, see the more detailed * comments in pngpriv.h */ /* The following is used internally to preserve the sticky flags */ #define png_fp_add(state, flags) ((state) |= (flags)) #define png_fp_set(state, value) ((state) = (value) | ((state) & PNG_FP_STICKY)) int /* PRIVATE */ png_check_fp_number(png_const_charp string, size_t size, int *statep, png_size_tp whereami) { int state = *statep; size_t i = *whereami; while (i < size) { int type; /* First find the type of the next character */ switch (string[i]) { case 43: type = PNG_FP_SAW_SIGN; break; case 45: type = PNG_FP_SAW_SIGN + PNG_FP_NEGATIVE; break; case 46: type = PNG_FP_SAW_DOT; break; case 48: type = PNG_FP_SAW_DIGIT; break; case 49: case 50: case 51: case 52: case 53: case 54: case 55: case 56: case 57: type = PNG_FP_SAW_DIGIT + PNG_FP_NONZERO; break; case 69: case 101: type = PNG_FP_SAW_E; break; default: goto PNG_FP_End; } /* Now deal with this type according to the current * state, the type is arranged to not overlap the * bits of the PNG_FP_STATE. */ switch ((state & PNG_FP_STATE) + (type & PNG_FP_SAW_ANY)) { case PNG_FP_INTEGER + PNG_FP_SAW_SIGN: if ((state & PNG_FP_SAW_ANY) != 0) goto PNG_FP_End; /* not a part of the number */ png_fp_add(state, type); break; case PNG_FP_INTEGER + PNG_FP_SAW_DOT: /* Ok as trailer, ok as lead of fraction. */ if ((state & PNG_FP_SAW_DOT) != 0) /* two dots */ goto PNG_FP_End; else if ((state & PNG_FP_SAW_DIGIT) != 0) /* trailing dot? */ png_fp_add(state, type); else png_fp_set(state, PNG_FP_FRACTION | type); break; case PNG_FP_INTEGER + PNG_FP_SAW_DIGIT: if ((state & PNG_FP_SAW_DOT) != 0) /* delayed fraction */ png_fp_set(state, PNG_FP_FRACTION | PNG_FP_SAW_DOT); png_fp_add(state, type | PNG_FP_WAS_VALID); break; case PNG_FP_INTEGER + PNG_FP_SAW_E: if ((state & PNG_FP_SAW_DIGIT) == 0) goto PNG_FP_End; png_fp_set(state, PNG_FP_EXPONENT); break; /* case PNG_FP_FRACTION + PNG_FP_SAW_SIGN: goto PNG_FP_End; ** no sign in fraction */ /* case PNG_FP_FRACTION + PNG_FP_SAW_DOT: goto PNG_FP_End; ** Because SAW_DOT is always set */ case PNG_FP_FRACTION + PNG_FP_SAW_DIGIT: png_fp_add(state, type | PNG_FP_WAS_VALID); break; case PNG_FP_FRACTION + PNG_FP_SAW_E: /* This is correct because the trailing '.' on an * integer is handled above - so we can only get here * with the sequence ".E" (with no preceding digits). */ if ((state & PNG_FP_SAW_DIGIT) == 0) goto PNG_FP_End; png_fp_set(state, PNG_FP_EXPONENT); break; case PNG_FP_EXPONENT + PNG_FP_SAW_SIGN: if ((state & PNG_FP_SAW_ANY) != 0) goto PNG_FP_End; /* not a part of the number */ png_fp_add(state, PNG_FP_SAW_SIGN); break; /* case PNG_FP_EXPONENT + PNG_FP_SAW_DOT: goto PNG_FP_End; */ case PNG_FP_EXPONENT + PNG_FP_SAW_DIGIT: png_fp_add(state, PNG_FP_SAW_DIGIT | PNG_FP_WAS_VALID); break; /* case PNG_FP_EXPONEXT + PNG_FP_SAW_E: goto PNG_FP_End; */ default: goto PNG_FP_End; /* I.e. break 2 */ } /* The character seems ok, continue. */ ++i; } PNG_FP_End: /* Here at the end, update the state and return the correct * return code. */ *statep = state; *whereami = i; return (state & PNG_FP_SAW_DIGIT) != 0; } /* The same but for a complete string. */ int png_check_fp_string(png_const_charp string, size_t size) { int state=0; size_t char_index=0; if (png_check_fp_number(string, size, &state, &char_index) != 0 && (char_index == size || string[char_index] == 0)) return state /* must be non-zero - see above */; return 0; /* i.e. fail */ } #endif /* pCAL || sCAL */ #ifdef PNG_sCAL_SUPPORTED # ifdef PNG_FLOATING_POINT_SUPPORTED /* Utility used below - a simple accurate power of ten from an integral * exponent. */ static double png_pow10(int power) { int recip = 0; double d = 1; /* Handle negative exponent with a reciprocal at the end because * 10 is exact whereas .1 is inexact in base 2 */ if (power < 0) { if (power < DBL_MIN_10_EXP) return 0; recip = 1; power = -power; } if (power > 0) { /* Decompose power bitwise. */ double mult = 10; do { if (power & 1) d *= mult; mult *= mult; power >>= 1; } while (power > 0); if (recip != 0) d = 1/d; } /* else power is 0 and d is 1 */ return d; } /* Function to format a floating point value in ASCII with a given * precision. */ #if GCC_STRICT_OVERFLOW #pragma GCC diagnostic push /* The problem arises below with exp_b10, which can never overflow because it * comes, originally, from frexp and is therefore limited to a range which is * typically +/-710 (log2(DBL_MAX)/log2(DBL_MIN)). */ #pragma GCC diagnostic warning "-Wstrict-overflow=2" #endif /* GCC_STRICT_OVERFLOW */ void /* PRIVATE */ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, size_t size, double fp, unsigned int precision) { /* We use standard functions from math.h, but not printf because * that would require stdio. The caller must supply a buffer of * sufficient size or we will png_error. The tests on size and * the space in ascii[] consumed are indicated below. */ if (precision < 1) precision = DBL_DIG; /* Enforce the limit of the implementation precision too. */ if (precision > DBL_DIG+1) precision = DBL_DIG+1; /* Basic sanity checks */ if (size >= precision+5) /* See the requirements below. */ { if (fp < 0) { fp = -fp; *ascii++ = 45; /* '-' PLUS 1 TOTAL 1 */ --size; } if (fp >= DBL_MIN && fp <= DBL_MAX) { int exp_b10; /* A base 10 exponent */ double base; /* 10^exp_b10 */ /* First extract a base 10 exponent of the number, * the calculation below rounds down when converting * from base 2 to base 10 (multiply by log10(2) - * 0.3010, but 77/256 is 0.3008, so exp_b10 needs to * be increased. Note that the arithmetic shift * performs a floor() unlike C arithmetic - using a * C multiply would break the following for negative * exponents. */ (void)frexp(fp, &exp_b10); /* exponent to base 2 */ exp_b10 = (exp_b10 * 77) >> 8; /* <= exponent to base 10 */ /* Avoid underflow here. */ base = png_pow10(exp_b10); /* May underflow */ while (base < DBL_MIN || base < fp) { /* And this may overflow. */ double test = png_pow10(exp_b10+1); if (test <= DBL_MAX) { ++exp_b10; base = test; } else break; } /* Normalize fp and correct exp_b10, after this fp is in the * range [.1,1) and exp_b10 is both the exponent and the digit * *before* which the decimal point should be inserted * (starting with 0 for the first digit). Note that this * works even if 10^exp_b10 is out of range because of the * test on DBL_MAX above. */ fp /= base; while (fp >= 1) { fp /= 10; ++exp_b10; } /* Because of the code above fp may, at this point, be * less than .1, this is ok because the code below can * handle the leading zeros this generates, so no attempt * is made to correct that here. */ { unsigned int czero, clead, cdigits; char exponent[10]; /* Allow up to two leading zeros - this will not lengthen * the number compared to using E-n. */ if (exp_b10 < 0 && exp_b10 > -3) /* PLUS 3 TOTAL 4 */ { czero = 0U-exp_b10; /* PLUS 2 digits: TOTAL 3 */ exp_b10 = 0; /* Dot added below before first output. */ } else czero = 0; /* No zeros to add */ /* Generate the digit list, stripping trailing zeros and * inserting a '.' before a digit if the exponent is 0. */ clead = czero; /* Count of leading zeros */ cdigits = 0; /* Count of digits in list. */ do { double d; fp *= 10; /* Use modf here, not floor and subtract, so that * the separation is done in one step. At the end * of the loop don't break the number into parts so * that the final digit is rounded. */ if (cdigits+czero+1 < precision+clead) fp = modf(fp, &d); else { d = floor(fp + .5); if (d > 9) { /* Rounding up to 10, handle that here. */ if (czero > 0) { --czero; d = 1; if (cdigits == 0) --clead; } else { while (cdigits > 0 && d > 9) { int ch = *--ascii; if (exp_b10 != (-1)) ++exp_b10; else if (ch == 46) { ch = *--ascii; ++size; /* Advance exp_b10 to '1', so that the * decimal point happens after the * previous digit. */ exp_b10 = 1; } --cdigits; d = ch - 47; /* I.e. 1+(ch-48) */ } /* Did we reach the beginning? If so adjust the * exponent but take into account the leading * decimal point. */ if (d > 9) /* cdigits == 0 */ { if (exp_b10 == (-1)) { /* Leading decimal point (plus zeros?), if * we lose the decimal point here it must * be reentered below. */ int ch = *--ascii; if (ch == 46) { ++size; exp_b10 = 1; } /* Else lost a leading zero, so 'exp_b10' is * still ok at (-1) */ } else ++exp_b10; /* In all cases we output a '1' */ d = 1; } } } fp = 0; /* Guarantees termination below. */ } if (d == 0) { ++czero; if (cdigits == 0) ++clead; } else { /* Included embedded zeros in the digit count. */ cdigits += czero - clead; clead = 0; while (czero > 0) { /* exp_b10 == (-1) means we just output the decimal * place - after the DP don't adjust 'exp_b10' any * more! */ if (exp_b10 != (-1)) { if (exp_b10 == 0) { *ascii++ = 46; --size; } /* PLUS 1: TOTAL 4 */ --exp_b10; } *ascii++ = 48; --czero; } if (exp_b10 != (-1)) { if (exp_b10 == 0) { *ascii++ = 46; --size; /* counted above */ } --exp_b10; } *ascii++ = (char)(48 + (int)d); ++cdigits; } } while (cdigits+czero < precision+clead && fp > DBL_MIN); /* The total output count (max) is now 4+precision */ /* Check for an exponent, if we don't need one we are * done and just need to terminate the string. At this * point, exp_b10==(-1) is effectively a flag: it got * to '-1' because of the decrement, after outputting * the decimal point above. (The exponent required is * *not* -1.) */ if (exp_b10 >= (-1) && exp_b10 <= 2) { /* The following only happens if we didn't output the * leading zeros above for negative exponent, so this * doesn't add to the digit requirement. Note that the * two zeros here can only be output if the two leading * zeros were *not* output, so this doesn't increase * the output count. */ while (exp_b10-- > 0) *ascii++ = 48; *ascii = 0; /* Total buffer requirement (including the '\0') is * 5+precision - see check at the start. */ return; } /* Here if an exponent is required, adjust size for * the digits we output but did not count. The total * digit output here so far is at most 1+precision - no * decimal point and no leading or trailing zeros have * been output. */ size -= cdigits; *ascii++ = 69; --size; /* 'E': PLUS 1 TOTAL 2+precision */ /* The following use of an unsigned temporary avoids ambiguities in * the signed arithmetic on exp_b10 and permits GCC at least to do * better optimization. */ { unsigned int uexp_b10; if (exp_b10 < 0) { *ascii++ = 45; --size; /* '-': PLUS 1 TOTAL 3+precision */ uexp_b10 = 0U-exp_b10; } else uexp_b10 = 0U+exp_b10; cdigits = 0; while (uexp_b10 > 0) { exponent[cdigits++] = (char)(48 + uexp_b10 % 10); uexp_b10 /= 10; } } /* Need another size check here for the exponent digits, so * this need not be considered above. */ if (size > cdigits) { while (cdigits > 0) *ascii++ = exponent[--cdigits]; *ascii = 0; return; } } } else if (!(fp >= DBL_MIN)) { *ascii++ = 48; /* '0' */ *ascii = 0; return; } else { *ascii++ = 105; /* 'i' */ *ascii++ = 110; /* 'n' */ *ascii++ = 102; /* 'f' */ *ascii = 0; return; } } /* Here on buffer too small. */ png_error(png_ptr, "ASCII conversion buffer too small"); } #if GCC_STRICT_OVERFLOW #pragma GCC diagnostic pop #endif /* GCC_STRICT_OVERFLOW */ # endif /* FLOATING_POINT */ # ifdef PNG_FIXED_POINT_SUPPORTED /* Function to format a fixed point value in ASCII. */ void /* PRIVATE */ png_ascii_from_fixed(png_const_structrp png_ptr, png_charp ascii, size_t size, png_fixed_point fp) { /* Require space for 10 decimal digits, a decimal point, a minus sign and a * trailing \0, 13 characters: */ if (size > 12) { png_uint_32 num; /* Avoid overflow here on the minimum integer. */ if (fp < 0) { *ascii++ = 45; num = (png_uint_32)(-fp); } else num = (png_uint_32)fp; if (num <= 0x80000000) /* else overflowed */ { unsigned int ndigits = 0, first = 16 /* flag value */; char digits[10]; while (num) { /* Split the low digit off num: */ unsigned int tmp = num/10; num -= tmp*10; digits[ndigits++] = (char)(48 + num); /* Record the first non-zero digit, note that this is a number * starting at 1, it's not actually the array index. */ if (first == 16 && num > 0) first = ndigits; num = tmp; } if (ndigits > 0) { while (ndigits > 5) *ascii++ = digits[--ndigits]; /* The remaining digits are fractional digits, ndigits is '5' or * smaller at this point. It is certainly not zero. Check for a * non-zero fractional digit: */ if (first <= 5) { unsigned int i; *ascii++ = 46; /* decimal point */ /* ndigits may be <5 for small numbers, output leading zeros * then ndigits digits to first: */ i = 5; while (ndigits < i) { *ascii++ = 48; --i; } while (ndigits >= first) *ascii++ = digits[--ndigits]; /* Don't output the trailing zeros! */ } } else *ascii++ = 48; /* And null terminate the string: */ *ascii = 0; return; } } /* Here on buffer too small. */ png_error(png_ptr, "ASCII conversion buffer too small"); } # endif /* FIXED_POINT */ #endif /* SCAL */ #if defined(PNG_FLOATING_POINT_SUPPORTED) && \ !defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \ (defined(PNG_gAMA_SUPPORTED) || defined(PNG_cHRM_SUPPORTED) || \ defined(PNG_sCAL_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) || \ defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)) || \ (defined(PNG_sCAL_SUPPORTED) && \ defined(PNG_FLOATING_ARITHMETIC_SUPPORTED)) png_fixed_point png_fixed(png_const_structrp png_ptr, double fp, png_const_charp text) { double r = floor(100000 * fp + .5); if (r > 2147483647. || r < -2147483648.) png_fixed_error(png_ptr, text); # ifndef PNG_ERROR_TEXT_SUPPORTED PNG_UNUSED(text) # endif return (png_fixed_point)r; } #endif #if defined(PNG_GAMMA_SUPPORTED) || defined(PNG_COLORSPACE_SUPPORTED) ||\ defined(PNG_INCH_CONVERSIONS_SUPPORTED) || defined(PNG_READ_pHYs_SUPPORTED) /* muldiv functions */ /* This API takes signed arguments and rounds the result to the nearest * integer (or, for a fixed point number - the standard argument - to * the nearest .00001). Overflow and divide by zero are signalled in * the result, a boolean - true on success, false on overflow. */ #if GCC_STRICT_OVERFLOW /* from above */ /* It is not obvious which comparison below gets optimized in such a way that * signed overflow would change the result; looking through the code does not * reveal any tests which have the form GCC complains about, so presumably the * optimizer is moving an add or subtract into the 'if' somewhere. */ #pragma GCC diagnostic push #pragma GCC diagnostic warning "-Wstrict-overflow=2" #endif /* GCC_STRICT_OVERFLOW */ int png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times, png_int_32 divisor) { /* Return a * times / divisor, rounded. */ if (divisor != 0) { if (a == 0 || times == 0) { *res = 0; return 1; } else { #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED double r = a; r *= times; r /= divisor; r = floor(r+.5); /* A png_fixed_point is a 32-bit integer. */ if (r <= 2147483647. && r >= -2147483648.) { *res = (png_fixed_point)r; return 1; } #else int negative = 0; png_uint_32 A, T, D; png_uint_32 s16, s32, s00; if (a < 0) negative = 1, A = -a; else A = a; if (times < 0) negative = !negative, T = -times; else T = times; if (divisor < 0) negative = !negative, D = -divisor; else D = divisor; /* Following can't overflow because the arguments only * have 31 bits each, however the result may be 32 bits. */ s16 = (A >> 16) * (T & 0xffff) + (A & 0xffff) * (T >> 16); /* Can't overflow because the a*times bit is only 30 * bits at most. */ s32 = (A >> 16) * (T >> 16) + (s16 >> 16); s00 = (A & 0xffff) * (T & 0xffff); s16 = (s16 & 0xffff) << 16; s00 += s16; if (s00 < s16) ++s32; /* carry */ if (s32 < D) /* else overflow */ { /* s32.s00 is now the 64-bit product, do a standard * division, we know that s32 < D, so the maximum * required shift is 31. */ int bitshift = 32; png_fixed_point result = 0; /* NOTE: signed */ while (--bitshift >= 0) { png_uint_32 d32, d00; if (bitshift > 0) d32 = D >> (32-bitshift), d00 = D << bitshift; else d32 = 0, d00 = D; if (s32 > d32) { if (s00 < d00) --s32; /* carry */ s32 -= d32, s00 -= d00, result += 1<<bitshift; } else if (s32 == d32 && s00 >= d00) s32 = 0, s00 -= d00, result += 1<<bitshift; } /* Handle the rounding. */ if (s00 >= (D >> 1)) ++result; if (negative != 0) result = -result; /* Check for overflow. */ if ((negative != 0 && result <= 0) || (negative == 0 && result >= 0)) { *res = result; return 1; } } #endif } } return 0; } #if GCC_STRICT_OVERFLOW #pragma GCC diagnostic pop #endif /* GCC_STRICT_OVERFLOW */ #endif /* READ_GAMMA || INCH_CONVERSIONS */ #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED) /* The following is for when the caller doesn't much care about the * result. */ png_fixed_point png_muldiv_warn(png_const_structrp png_ptr, png_fixed_point a, png_int_32 times, png_int_32 divisor) { png_fixed_point result; if (png_muldiv(&result, a, times, divisor) != 0) return result; png_warning(png_ptr, "fixed point overflow ignored"); return 0; } #endif #ifdef PNG_GAMMA_SUPPORTED /* more fixed point functions for gamma */ /* Calculate a reciprocal, return 0 on div-by-zero or overflow. */ png_fixed_point png_reciprocal(png_fixed_point a) { #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED double r = floor(1E10/a+.5); if (r <= 2147483647. && r >= -2147483648.) return (png_fixed_point)r; #else png_fixed_point res; if (png_muldiv(&res, 100000, 100000, a) != 0) return res; #endif return 0; /* error/overflow */ } /* This is the shared test on whether a gamma value is 'significant' - whether * it is worth doing gamma correction. */ int /* PRIVATE */ png_gamma_significant(png_fixed_point gamma_val) { return gamma_val < PNG_FP_1 - PNG_GAMMA_THRESHOLD_FIXED || gamma_val > PNG_FP_1 + PNG_GAMMA_THRESHOLD_FIXED; } #endif #ifdef PNG_READ_GAMMA_SUPPORTED #ifdef PNG_16BIT_SUPPORTED /* A local convenience routine. */ static png_fixed_point png_product2(png_fixed_point a, png_fixed_point b) { /* The required result is 1/a * 1/b; the following preserves accuracy. */ #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED double r = a * 1E-5; r *= b; r = floor(r+.5); if (r <= 2147483647. && r >= -2147483648.) return (png_fixed_point)r; #else png_fixed_point res; if (png_muldiv(&res, a, b, 100000) != 0) return res; #endif return 0; /* overflow */ } #endif /* 16BIT */ /* The inverse of the above. */ png_fixed_point png_reciprocal2(png_fixed_point a, png_fixed_point b) { /* The required result is 1/a * 1/b; the following preserves accuracy. */ #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED if (a != 0 && b != 0) { double r = 1E15/a; r /= b; r = floor(r+.5); if (r <= 2147483647. && r >= -2147483648.) return (png_fixed_point)r; } #else /* This may overflow because the range of png_fixed_point isn't symmetric, * but this API is only used for the product of file and screen gamma so it * doesn't matter that the smallest number it can produce is 1/21474, not * 1/100000 */ png_fixed_point res = png_product2(a, b); if (res != 0) return png_reciprocal(res); #endif return 0; /* overflow */ } #endif /* READ_GAMMA */ #ifdef PNG_READ_GAMMA_SUPPORTED /* gamma table code */ #ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED /* Fixed point gamma. * * The code to calculate the tables used below can be found in the shell script * contrib/tools/intgamma.sh * * To calculate gamma this code implements fast log() and exp() calls using only * fixed point arithmetic. This code has sufficient precision for either 8-bit * or 16-bit sample values. * * The tables used here were calculated using simple 'bc' programs, but C double * precision floating point arithmetic would work fine. * * 8-bit log table * This is a table of -log(value/255)/log(2) for 'value' in the range 128 to * 255, so it's the base 2 logarithm of a normalized 8-bit floating point * mantissa. The numbers are 32-bit fractions. */ static const png_uint_32 png_8bit_l2[128] = { 4270715492U, 4222494797U, 4174646467U, 4127164793U, 4080044201U, 4033279239U, 3986864580U, 3940795015U, 3895065449U, 3849670902U, 3804606499U, 3759867474U, 3715449162U, 3671346997U, 3627556511U, 3584073329U, 3540893168U, 3498011834U, 3455425220U, 3413129301U, 3371120137U, 3329393864U, 3287946700U, 3246774933U, 3205874930U, 3165243125U, 3124876025U, 3084770202U, 3044922296U, 3005329011U, 2965987113U, 2926893432U, 2888044853U, 2849438323U, 2811070844U, 2772939474U, 2735041326U, 2697373562U, 2659933400U, 2622718104U, 2585724991U, 2548951424U, 2512394810U, 2476052606U, 2439922311U, 2404001468U, 2368287663U, 2332778523U, 2297471715U, 2262364947U, 2227455964U, 2192742551U, 2158222529U, 2123893754U, 2089754119U, 2055801552U, 2022034013U, 1988449497U, 1955046031U, 1921821672U, 1888774511U, 1855902668U, 1823204291U, 1790677560U, 1758320682U, 1726131893U, 1694109454U, 1662251657U, 1630556815U, 1599023271U, 1567649391U, 1536433567U, 1505374214U, 1474469770U, 1443718700U, 1413119487U, 1382670639U, 1352370686U, 1322218179U, 1292211689U, 1262349810U, 1232631153U, 1203054352U, 1173618059U, 1144320946U, 1115161701U, 1086139034U, 1057251672U, 1028498358U, 999877854U, 971388940U, 943030410U, 914801076U, 886699767U, 858725327U, 830876614U, 803152505U, 775551890U, 748073672U, 720716771U, 693480120U, 666362667U, 639363374U, 612481215U, 585715177U, 559064263U, 532527486U, 506103872U, 479792461U, 453592303U, 427502463U, 401522014U, 375650043U, 349885648U, 324227938U, 298676034U, 273229066U, 247886176U, 222646516U, 197509248U, 172473545U, 147538590U, 122703574U, 97967701U, 73330182U, 48790236U, 24347096U, 0U #if 0 /* The following are the values for 16-bit tables - these work fine for the * 8-bit conversions but produce very slightly larger errors in the 16-bit * log (about 1.2 as opposed to 0.7 absolute error in the final value). To * use these all the shifts below must be adjusted appropriately. */ 65166, 64430, 63700, 62976, 62257, 61543, 60835, 60132, 59434, 58741, 58054, 57371, 56693, 56020, 55352, 54689, 54030, 53375, 52726, 52080, 51439, 50803, 50170, 49542, 48918, 48298, 47682, 47070, 46462, 45858, 45257, 44661, 44068, 43479, 42894, 42312, 41733, 41159, 40587, 40020, 39455, 38894, 38336, 37782, 37230, 36682, 36137, 35595, 35057, 34521, 33988, 33459, 32932, 32408, 31887, 31369, 30854, 30341, 29832, 29325, 28820, 28319, 27820, 27324, 26830, 26339, 25850, 25364, 24880, 24399, 23920, 23444, 22970, 22499, 22029, 21562, 21098, 20636, 20175, 19718, 19262, 18808, 18357, 17908, 17461, 17016, 16573, 16132, 15694, 15257, 14822, 14390, 13959, 13530, 13103, 12678, 12255, 11834, 11415, 10997, 10582, 10168, 9756, 9346, 8937, 8531, 8126, 7723, 7321, 6921, 6523, 6127, 5732, 5339, 4947, 4557, 4169, 3782, 3397, 3014, 2632, 2251, 1872, 1495, 1119, 744, 372 #endif }; static png_int_32 png_log8bit(unsigned int x) { unsigned int lg2 = 0; /* Each time 'x' is multiplied by 2, 1 must be subtracted off the final log, * because the log is actually negate that means adding 1. The final * returned value thus has the range 0 (for 255 input) to 7.994 (for 1 * input), return -1 for the overflow (log 0) case, - so the result is * always at most 19 bits. */ if ((x &= 0xff) == 0) return -1; if ((x & 0xf0) == 0) lg2 = 4, x <<= 4; if ((x & 0xc0) == 0) lg2 += 2, x <<= 2; if ((x & 0x80) == 0) lg2 += 1, x <<= 1; /* result is at most 19 bits, so this cast is safe: */ return (png_int_32)((lg2 << 16) + ((png_8bit_l2[x-128]+32768)>>16)); } /* The above gives exact (to 16 binary places) log2 values for 8-bit images, * for 16-bit images we use the most significant 8 bits of the 16-bit value to * get an approximation then multiply the approximation by a correction factor * determined by the remaining up to 8 bits. This requires an additional step * in the 16-bit case. * * We want log2(value/65535), we have log2(v'/255), where: * * value = v' * 256 + v'' * = v' * f * * So f is value/v', which is equal to (256+v''/v') since v' is in the range 128 * to 255 and v'' is in the range 0 to 255 f will be in the range 256 to less * than 258. The final factor also needs to correct for the fact that our 8-bit * value is scaled by 255, whereas the 16-bit values must be scaled by 65535. * * This gives a final formula using a calculated value 'x' which is value/v' and * scaling by 65536 to match the above table: * * log2(x/257) * 65536 * * Since these numbers are so close to '1' we can use simple linear * interpolation between the two end values 256/257 (result -368.61) and 258/257 * (result 367.179). The values used below are scaled by a further 64 to give * 16-bit precision in the interpolation: * * Start (256): -23591 * Zero (257): 0 * End (258): 23499 */ #ifdef PNG_16BIT_SUPPORTED static png_int_32 png_log16bit(png_uint_32 x) { unsigned int lg2 = 0; /* As above, but now the input has 16 bits. */ if ((x &= 0xffff) == 0) return -1; if ((x & 0xff00) == 0) lg2 = 8, x <<= 8; if ((x & 0xf000) == 0) lg2 += 4, x <<= 4; if ((x & 0xc000) == 0) lg2 += 2, x <<= 2; if ((x & 0x8000) == 0) lg2 += 1, x <<= 1; /* Calculate the base logarithm from the top 8 bits as a 28-bit fractional * value. */ lg2 <<= 28; lg2 += (png_8bit_l2[(x>>8)-128]+8) >> 4; /* Now we need to interpolate the factor, this requires a division by the top * 8 bits. Do this with maximum precision. */ x = ((x << 16) + (x >> 9)) / (x >> 8); /* Since we divided by the top 8 bits of 'x' there will be a '1' at 1<<24, * the value at 1<<16 (ignoring this) will be 0 or 1; this gives us exactly * 16 bits to interpolate to get the low bits of the result. Round the * answer. Note that the end point values are scaled by 64 to retain overall * precision and that 'lg2' is current scaled by an extra 12 bits, so adjust * the overall scaling by 6-12. Round at every step. */ x -= 1U << 24; if (x <= 65536U) /* <= '257' */ lg2 += ((23591U * (65536U-x)) + (1U << (16+6-12-1))) >> (16+6-12); else lg2 -= ((23499U * (x-65536U)) + (1U << (16+6-12-1))) >> (16+6-12); /* Safe, because the result can't have more than 20 bits: */ return (png_int_32)((lg2 + 2048) >> 12); } #endif /* 16BIT */ /* The 'exp()' case must invert the above, taking a 20-bit fixed point * logarithmic value and returning a 16 or 8-bit number as appropriate. In * each case only the low 16 bits are relevant - the fraction - since the * integer bits (the top 4) simply determine a shift. * * The worst case is the 16-bit distinction between 65535 and 65534. This * requires perhaps spurious accuracy in the decoding of the logarithm to * distinguish log2(65535/65534.5) - 10^-5 or 17 bits. There is little chance * of getting this accuracy in practice. * * To deal with this the following exp() function works out the exponent of the * fractional part of the logarithm by using an accurate 32-bit value from the * top four fractional bits then multiplying in the remaining bits. */ static const png_uint_32 png_32bit_exp[16] = { /* NOTE: the first entry is deliberately set to the maximum 32-bit value. */ 4294967295U, 4112874773U, 3938502376U, 3771522796U, 3611622603U, 3458501653U, 3311872529U, 3171459999U, 3037000500U, 2908241642U, 2784941738U, 2666869345U, 2553802834U, 2445529972U, 2341847524U, 2242560872U }; /* Adjustment table; provided to explain the numbers in the code below. */ #if 0 for (i=11;i>=0;--i){ print i, " ", (1 - e(-(2^i)/65536*l(2))) * 2^(32-i), "\n"} 11 44937.64284865548751208448 10 45180.98734845585101160448 9 45303.31936980687359311872 8 45364.65110595323018870784 7 45395.35850361789624614912 6 45410.72259715102037508096 5 45418.40724413220722311168 4 45422.25021786898173001728 3 45424.17186732298419044352 2 45425.13273269940811464704 1 45425.61317555035558641664 0 45425.85339951654943850496 #endif static png_uint_32 png_exp(png_fixed_point x) { if (x > 0 && x <= 0xfffff) /* Else overflow or zero (underflow) */ { /* Obtain a 4-bit approximation */ png_uint_32 e = png_32bit_exp[(x >> 12) & 0x0f]; /* Incorporate the low 12 bits - these decrease the returned value by * multiplying by a number less than 1 if the bit is set. The multiplier * is determined by the above table and the shift. Notice that the values * converge on 45426 and this is used to allow linear interpolation of the * low bits. */ if (x & 0x800) e -= (((e >> 16) * 44938U) + 16U) >> 5; if (x & 0x400) e -= (((e >> 16) * 45181U) + 32U) >> 6; if (x & 0x200) e -= (((e >> 16) * 45303U) + 64U) >> 7; if (x & 0x100) e -= (((e >> 16) * 45365U) + 128U) >> 8; if (x & 0x080) e -= (((e >> 16) * 45395U) + 256U) >> 9; if (x & 0x040) e -= (((e >> 16) * 45410U) + 512U) >> 10; /* And handle the low 6 bits in a single block. */ e -= (((e >> 16) * 355U * (x & 0x3fU)) + 256U) >> 9; /* Handle the upper bits of x. */ e >>= x >> 16; return e; } /* Check for overflow */ if (x <= 0) return png_32bit_exp[0]; /* Else underflow */ return 0; } static png_byte png_exp8bit(png_fixed_point lg2) { /* Get a 32-bit value: */ png_uint_32 x = png_exp(lg2); /* Convert the 32-bit value to 0..255 by multiplying by 256-1. Note that the * second, rounding, step can't overflow because of the first, subtraction, * step. */ x -= x >> 8; return (png_byte)(((x + 0x7fffffU) >> 24) & 0xff); } #ifdef PNG_16BIT_SUPPORTED static png_uint_16 png_exp16bit(png_fixed_point lg2) { /* Get a 32-bit value: */ png_uint_32 x = png_exp(lg2); /* Convert the 32-bit value to 0..65535 by multiplying by 65536-1: */ x -= x >> 16; return (png_uint_16)((x + 32767U) >> 16); } #endif /* 16BIT */ #endif /* FLOATING_ARITHMETIC */ png_byte png_gamma_8bit_correct(unsigned int value, png_fixed_point gamma_val) { if (value > 0 && value < 255) { # ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED /* 'value' is unsigned, ANSI-C90 requires the compiler to correctly * convert this to a floating point value. This includes values that * would overflow if 'value' were to be converted to 'int'. * * Apparently GCC, however, does an intermediate conversion to (int) * on some (ARM) but not all (x86) platforms, possibly because of * hardware FP limitations. (E.g. if the hardware conversion always * assumes the integer register contains a signed value.) This results * in ANSI-C undefined behavior for large values. * * Other implementations on the same machine might actually be ANSI-C90 * conformant and therefore compile spurious extra code for the large * values. * * We can be reasonably sure that an unsigned to float conversion * won't be faster than an int to float one. Therefore this code * assumes responsibility for the undefined behavior, which it knows * can't happen because of the check above. * * Note the argument to this routine is an (unsigned int) because, on * 16-bit platforms, it is assigned a value which might be out of * range for an (int); that would result in undefined behavior in the * caller if the *argument* ('value') were to be declared (int). */ double r = floor(255*pow((int)/*SAFE*/value/255.,gamma_val*.00001)+.5); return (png_byte)r; # else png_int_32 lg2 = png_log8bit(value); png_fixed_point res; if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) != 0) return png_exp8bit(res); /* Overflow. */ value = 0; # endif } return (png_byte)(value & 0xff); } #ifdef PNG_16BIT_SUPPORTED png_uint_16 png_gamma_16bit_correct(unsigned int value, png_fixed_point gamma_val) { if (value > 0 && value < 65535) { # ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED /* The same (unsigned int)->(double) constraints apply here as above, * however in this case the (unsigned int) to (int) conversion can * overflow on an ANSI-C90 compliant system so the cast needs to ensure * that this is not possible. */ double r = floor(65535*pow((png_int_32)value/65535., gamma_val*.00001)+.5); return (png_uint_16)r; # else png_int_32 lg2 = png_log16bit(value); png_fixed_point res; if (png_muldiv(&res, gamma_val, lg2, PNG_FP_1) != 0) return png_exp16bit(res); /* Overflow. */ value = 0; # endif } return (png_uint_16)value; } #endif /* 16BIT */ /* This does the right thing based on the bit_depth field of the * png_struct, interpreting values as 8-bit or 16-bit. While the result * is nominally a 16-bit value if bit depth is 8 then the result is * 8-bit (as are the arguments.) */ png_uint_16 /* PRIVATE */ png_gamma_correct(png_structrp png_ptr, unsigned int value, png_fixed_point gamma_val) { if (png_ptr->bit_depth == 8) return png_gamma_8bit_correct(value, gamma_val); #ifdef PNG_16BIT_SUPPORTED else return png_gamma_16bit_correct(value, gamma_val); #else /* should not reach this */ return 0; #endif /* 16BIT */ } #ifdef PNG_16BIT_SUPPORTED /* Internal function to build a single 16-bit table - the table consists of * 'num' 256 entry subtables, where 'num' is determined by 'shift' - the amount * to shift the input values right (or 16-number_of_signifiant_bits). * * The caller is responsible for ensuring that the table gets cleaned up on * png_error (i.e. if one of the mallocs below fails) - i.e. the *table argument * should be somewhere that will be cleaned. */ static void png_build_16bit_table(png_structrp png_ptr, png_uint_16pp *ptable, unsigned int shift, png_fixed_point gamma_val) { /* Various values derived from 'shift': */ unsigned int num = 1U << (8U - shift); #ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED /* CSE the division and work round wacky GCC warnings (see the comments * in png_gamma_8bit_correct for where these come from.) */ double fmax = 1.0 / (((png_int_32)1 << (16U - shift)) - 1); #endif unsigned int max = (1U << (16U - shift)) - 1U; unsigned int max_by_2 = 1U << (15U - shift); unsigned int i; png_uint_16pp table = *ptable = (png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p))); for (i = 0; i < num; i++) { png_uint_16p sub_table = table[i] = (png_uint_16p)png_malloc(png_ptr, 256 * (sizeof (png_uint_16))); /* The 'threshold' test is repeated here because it can arise for one of * the 16-bit tables even if the others don't hit it. */ if (png_gamma_significant(gamma_val) != 0) { /* The old code would overflow at the end and this would cause the * 'pow' function to return a result >1, resulting in an * arithmetic error. This code follows the spec exactly; ig is * the recovered input sample, it always has 8-16 bits. * * We want input * 65535/max, rounded, the arithmetic fits in 32 * bits (unsigned) so long as max <= 32767. */ unsigned int j; for (j = 0; j < 256; j++) { png_uint_32 ig = (j << (8-shift)) + i; # ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED /* Inline the 'max' scaling operation: */ /* See png_gamma_8bit_correct for why the cast to (int) is * required here. */ double d = floor(65535.*pow(ig*fmax, gamma_val*.00001)+.5); sub_table[j] = (png_uint_16)d; # else if (shift != 0) ig = (ig * 65535U + max_by_2)/max; sub_table[j] = png_gamma_16bit_correct(ig, gamma_val); # endif } } else { /* We must still build a table, but do it the fast way. */ unsigned int j; for (j = 0; j < 256; j++) { png_uint_32 ig = (j << (8-shift)) + i; if (shift != 0) ig = (ig * 65535U + max_by_2)/max; sub_table[j] = (png_uint_16)ig; } } } } /* NOTE: this function expects the *inverse* of the overall gamma transformation * required. */ static void png_build_16to8_table(png_structrp png_ptr, png_uint_16pp *ptable, unsigned int shift, png_fixed_point gamma_val) { unsigned int num = 1U << (8U - shift); unsigned int max = (1U << (16U - shift))-1U; unsigned int i; png_uint_32 last; png_uint_16pp table = *ptable = (png_uint_16pp)png_calloc(png_ptr, num * (sizeof (png_uint_16p))); /* 'num' is the number of tables and also the number of low bits of low * bits of the input 16-bit value used to select a table. Each table is * itself indexed by the high 8 bits of the value. */ for (i = 0; i < num; i++) table[i] = (png_uint_16p)png_malloc(png_ptr, 256 * (sizeof (png_uint_16))); /* 'gamma_val' is set to the reciprocal of the value calculated above, so * pow(out,g) is an *input* value. 'last' is the last input value set. * * In the loop 'i' is used to find output values. Since the output is * 8-bit there are only 256 possible values. The tables are set up to * select the closest possible output value for each input by finding * the input value at the boundary between each pair of output values * and filling the table up to that boundary with the lower output * value. * * The boundary values are 0.5,1.5..253.5,254.5. Since these are 9-bit * values the code below uses a 16-bit value in i; the values start at * 128.5 (for 0.5) and step by 257, for a total of 254 values (the last * entries are filled with 255). Start i at 128 and fill all 'last' * table entries <= 'max' */ last = 0; for (i = 0; i < 255; ++i) /* 8-bit output value */ { /* Find the corresponding maximum input value */ png_uint_16 out = (png_uint_16)(i * 257U); /* 16-bit output value */ /* Find the boundary value in 16 bits: */ png_uint_32 bound = png_gamma_16bit_correct(out+128U, gamma_val); /* Adjust (round) to (16-shift) bits: */ bound = (bound * max + 32768U)/65535U + 1U; while (last < bound) { table[last & (0xffU >> shift)][last >> (8U - shift)] = out; last++; } } /* And fill in the final entries. */ while (last < (num << 8)) { table[last & (0xff >> shift)][last >> (8U - shift)] = 65535U; last++; } } #endif /* 16BIT */ /* Build a single 8-bit table: same as the 16-bit case but much simpler (and * typically much faster). Note that libpng currently does no sBIT processing * (apparently contrary to the spec) so a 256-entry table is always generated. */ static void png_build_8bit_table(png_structrp png_ptr, png_bytepp ptable, png_fixed_point gamma_val) { unsigned int i; png_bytep table = *ptable = (png_bytep)png_malloc(png_ptr, 256); if (png_gamma_significant(gamma_val) != 0) for (i=0; i<256; i++) table[i] = png_gamma_8bit_correct(i, gamma_val); else for (i=0; i<256; ++i) table[i] = (png_byte)(i & 0xff); } /* Used from png_read_destroy and below to release the memory used by the gamma * tables. */ void /* PRIVATE */ png_destroy_gamma_table(png_structrp png_ptr) { png_free(png_ptr, png_ptr->gamma_table); png_ptr->gamma_table = NULL; #ifdef PNG_16BIT_SUPPORTED if (png_ptr->gamma_16_table != NULL) { int i; int istop = (1 << (8 - png_ptr->gamma_shift)); for (i = 0; i < istop; i++) { png_free(png_ptr, png_ptr->gamma_16_table[i]); } png_free(png_ptr, png_ptr->gamma_16_table); png_ptr->gamma_16_table = NULL; } #endif /* 16BIT */ #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \ defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \ defined(PNG_READ_RGB_TO_GRAY_SUPPORTED) png_free(png_ptr, png_ptr->gamma_from_1); png_ptr->gamma_from_1 = NULL; png_free(png_ptr, png_ptr->gamma_to_1); png_ptr->gamma_to_1 = NULL; #ifdef PNG_16BIT_SUPPORTED if (png_ptr->gamma_16_from_1 != NULL) { int i; int istop = (1 << (8 - png_ptr->gamma_shift)); for (i = 0; i < istop; i++) { png_free(png_ptr, png_ptr->gamma_16_from_1[i]); } png_free(png_ptr, png_ptr->gamma_16_from_1); png_ptr->gamma_16_from_1 = NULL; } if (png_ptr->gamma_16_to_1 != NULL) { int i; int istop = (1 << (8 - png_ptr->gamma_shift)); for (i = 0; i < istop; i++) { png_free(png_ptr, png_ptr->gamma_16_to_1[i]); } png_free(png_ptr, png_ptr->gamma_16_to_1); png_ptr->gamma_16_to_1 = NULL; } #endif /* 16BIT */ #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */ } /* We build the 8- or 16-bit gamma tables here. Note that for 16-bit * tables, we don't make a full table if we are reducing to 8-bit in * the future. Note also how the gamma_16 tables are segmented so that * we don't need to allocate > 64K chunks for a full 16-bit table. */ void /* PRIVATE */ png_build_gamma_table(png_structrp png_ptr, int bit_depth) { png_debug(1, "in png_build_gamma_table"); /* Remove any existing table; this copes with multiple calls to * png_read_update_info. The warning is because building the gamma tables * multiple times is a performance hit - it's harmless but the ability to * call png_read_update_info() multiple times is new in 1.5.6 so it seems * sensible to warn if the app introduces such a hit. */ if (png_ptr->gamma_table != NULL || png_ptr->gamma_16_table != NULL) { png_warning(png_ptr, "gamma table being rebuilt"); png_destroy_gamma_table(png_ptr); } if (bit_depth <= 8) { png_build_8bit_table(png_ptr, &png_ptr->gamma_table, png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->colorspace.gamma, png_ptr->screen_gamma) : PNG_FP_1); #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \ defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \ defined(PNG_READ_RGB_TO_GRAY_SUPPORTED) if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) != 0) { png_build_8bit_table(png_ptr, &png_ptr->gamma_to_1, png_reciprocal(png_ptr->colorspace.gamma)); png_build_8bit_table(png_ptr, &png_ptr->gamma_from_1, png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) : png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */); } #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */ } #ifdef PNG_16BIT_SUPPORTED else { png_byte shift, sig_bit; if ((png_ptr->color_type & PNG_COLOR_MASK_COLOR) != 0) { sig_bit = png_ptr->sig_bit.red; if (png_ptr->sig_bit.green > sig_bit) sig_bit = png_ptr->sig_bit.green; if (png_ptr->sig_bit.blue > sig_bit) sig_bit = png_ptr->sig_bit.blue; } else sig_bit = png_ptr->sig_bit.gray; /* 16-bit gamma code uses this equation: * * ov = table[(iv & 0xff) >> gamma_shift][iv >> 8] * * Where 'iv' is the input color value and 'ov' is the output value - * pow(iv, gamma). * * Thus the gamma table consists of up to 256 256-entry tables. The table * is selected by the (8-gamma_shift) most significant of the low 8 bits * of the color value then indexed by the upper 8 bits: * * table[low bits][high 8 bits] * * So the table 'n' corresponds to all those 'iv' of: * * <all high 8-bit values><n << gamma_shift>..<(n+1 << gamma_shift)-1> * */ if (sig_bit > 0 && sig_bit < 16U) /* shift == insignificant bits */ shift = (png_byte)((16U - sig_bit) & 0xff); else shift = 0; /* keep all 16 bits */ if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0) { /* PNG_MAX_GAMMA_8 is the number of bits to keep - effectively * the significant bits in the *input* when the output will * eventually be 8 bits. By default it is 11. */ if (shift < (16U - PNG_MAX_GAMMA_8)) shift = (16U - PNG_MAX_GAMMA_8); } if (shift > 8U) shift = 8U; /* Guarantees at least one table! */ png_ptr->gamma_shift = shift; /* NOTE: prior to 1.5.4 this test used to include PNG_BACKGROUND (now * PNG_COMPOSE). This effectively smashed the background calculation for * 16-bit output because the 8-bit table assumes the result will be * reduced to 8 bits. */ if ((png_ptr->transformations & (PNG_16_TO_8 | PNG_SCALE_16_TO_8)) != 0) png_build_16to8_table(png_ptr, &png_ptr->gamma_16_table, shift, png_ptr->screen_gamma > 0 ? png_product2(png_ptr->colorspace.gamma, png_ptr->screen_gamma) : PNG_FP_1); else png_build_16bit_table(png_ptr, &png_ptr->gamma_16_table, shift, png_ptr->screen_gamma > 0 ? png_reciprocal2(png_ptr->colorspace.gamma, png_ptr->screen_gamma) : PNG_FP_1); #if defined(PNG_READ_BACKGROUND_SUPPORTED) || \ defined(PNG_READ_ALPHA_MODE_SUPPORTED) || \ defined(PNG_READ_RGB_TO_GRAY_SUPPORTED) if ((png_ptr->transformations & (PNG_COMPOSE | PNG_RGB_TO_GRAY)) != 0) { png_build_16bit_table(png_ptr, &png_ptr->gamma_16_to_1, shift, png_reciprocal(png_ptr->colorspace.gamma)); /* Notice that the '16 from 1' table should be full precision, however * the lookup on this table still uses gamma_shift, so it can't be. * TODO: fix this. */ png_build_16bit_table(png_ptr, &png_ptr->gamma_16_from_1, shift, png_ptr->screen_gamma > 0 ? png_reciprocal(png_ptr->screen_gamma) : png_ptr->colorspace.gamma/* Probably doing rgb_to_gray */); } #endif /* READ_BACKGROUND || READ_ALPHA_MODE || RGB_TO_GRAY */ } #endif /* 16BIT */ } #endif /* READ_GAMMA */ /* HARDWARE OR SOFTWARE OPTION SUPPORT */ #ifdef PNG_SET_OPTION_SUPPORTED int PNGAPI png_set_option(png_structrp png_ptr, int option, int onoff) { if (png_ptr != NULL && option >= 0 && option < PNG_OPTION_NEXT && (option & 1) == 0) { png_uint_32 mask = 3U << option; png_uint_32 setting = (2U + (onoff != 0)) << option; png_uint_32 current = png_ptr->options; png_ptr->options = (png_uint_32)((current & ~mask) | setting); return (int)(current & mask) >> option; } return PNG_OPTION_INVALID; } #endif /* sRGB support */ #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\ defined(PNG_SIMPLIFIED_WRITE_SUPPORTED) /* sRGB conversion tables; these are machine generated with the code in * contrib/tools/makesRGB.c. The actual sRGB transfer curve defined in the * specification (see the article at https://en.wikipedia.org/wiki/SRGB) * is used, not the gamma=1/2.2 approximation use elsewhere in libpng. * The sRGB to linear table is exact (to the nearest 16-bit linear fraction). * The inverse (linear to sRGB) table has accuracies as follows: * * For all possible (255*65535+1) input values: * * error: -0.515566 - 0.625971, 79441 (0.475369%) of readings inexact * * For the input values corresponding to the 65536 16-bit values: * * error: -0.513727 - 0.607759, 308 (0.469978%) of readings inexact * * In all cases the inexact readings are only off by one. */ #ifdef PNG_SIMPLIFIED_READ_SUPPORTED /* The convert-to-sRGB table is only currently required for read. */ const png_uint_16 png_sRGB_table[256] = { 0,20,40,60,80,99,119,139, 159,179,199,219,241,264,288,313, 340,367,396,427,458,491,526,562, 599,637,677,718,761,805,851,898, 947,997,1048,1101,1156,1212,1270,1330, 1391,1453,1517,1583,1651,1720,1790,1863, 1937,2013,2090,2170,2250,2333,2418,2504, 2592,2681,2773,2866,2961,3058,3157,3258, 3360,3464,3570,3678,3788,3900,4014,4129, 4247,4366,4488,4611,4736,4864,4993,5124, 5257,5392,5530,5669,5810,5953,6099,6246, 6395,6547,6700,6856,7014,7174,7335,7500, 7666,7834,8004,8177,8352,8528,8708,8889, 9072,9258,9445,9635,9828,10022,10219,10417, 10619,10822,11028,11235,11446,11658,11873,12090, 12309,12530,12754,12980,13209,13440,13673,13909, 14146,14387,14629,14874,15122,15371,15623,15878, 16135,16394,16656,16920,17187,17456,17727,18001, 18277,18556,18837,19121,19407,19696,19987,20281, 20577,20876,21177,21481,21787,22096,22407,22721, 23038,23357,23678,24002,24329,24658,24990,25325, 25662,26001,26344,26688,27036,27386,27739,28094, 28452,28813,29176,29542,29911,30282,30656,31033, 31412,31794,32179,32567,32957,33350,33745,34143, 34544,34948,35355,35764,36176,36591,37008,37429, 37852,38278,38706,39138,39572,40009,40449,40891, 41337,41785,42236,42690,43147,43606,44069,44534, 45002,45473,45947,46423,46903,47385,47871,48359, 48850,49344,49841,50341,50844,51349,51858,52369, 52884,53401,53921,54445,54971,55500,56032,56567, 57105,57646,58190,58737,59287,59840,60396,60955, 61517,62082,62650,63221,63795,64372,64952,65535 }; #endif /* SIMPLIFIED_READ */ /* The base/delta tables are required for both read and write (but currently * only the simplified versions.) */ const png_uint_16 png_sRGB_base[512] = { 128,1782,3383,4644,5675,6564,7357,8074, 8732,9346,9921,10463,10977,11466,11935,12384, 12816,13233,13634,14024,14402,14769,15125,15473, 15812,16142,16466,16781,17090,17393,17690,17981, 18266,18546,18822,19093,19359,19621,19879,20133, 20383,20630,20873,21113,21349,21583,21813,22041, 22265,22487,22707,22923,23138,23350,23559,23767, 23972,24175,24376,24575,24772,24967,25160,25352, 25542,25730,25916,26101,26284,26465,26645,26823, 27000,27176,27350,27523,27695,27865,28034,28201, 28368,28533,28697,28860,29021,29182,29341,29500, 29657,29813,29969,30123,30276,30429,30580,30730, 30880,31028,31176,31323,31469,31614,31758,31902, 32045,32186,32327,32468,32607,32746,32884,33021, 33158,33294,33429,33564,33697,33831,33963,34095, 34226,34357,34486,34616,34744,34873,35000,35127, 35253,35379,35504,35629,35753,35876,35999,36122, 36244,36365,36486,36606,36726,36845,36964,37083, 37201,37318,37435,37551,37668,37783,37898,38013, 38127,38241,38354,38467,38580,38692,38803,38915, 39026,39136,39246,39356,39465,39574,39682,39790, 39898,40005,40112,40219,40325,40431,40537,40642, 40747,40851,40955,41059,41163,41266,41369,41471, 41573,41675,41777,41878,41979,42079,42179,42279, 42379,42478,42577,42676,42775,42873,42971,43068, 43165,43262,43359,43456,43552,43648,43743,43839, 43934,44028,44123,44217,44311,44405,44499,44592, 44685,44778,44870,44962,45054,45146,45238,45329, 45420,45511,45601,45692,45782,45872,45961,46051, 46140,46229,46318,46406,46494,46583,46670,46758, 46846,46933,47020,47107,47193,47280,47366,47452, 47538,47623,47709,47794,47879,47964,48048,48133, 48217,48301,48385,48468,48552,48635,48718,48801, 48884,48966,49048,49131,49213,49294,49376,49458, 49539,49620,49701,49782,49862,49943,50023,50103, 50183,50263,50342,50422,50501,50580,50659,50738, 50816,50895,50973,51051,51129,51207,51285,51362, 51439,51517,51594,51671,51747,51824,51900,51977, 52053,52129,52205,52280,52356,52432,52507,52582, 52657,52732,52807,52881,52956,53030,53104,53178, 53252,53326,53400,53473,53546,53620,53693,53766, 53839,53911,53984,54056,54129,54201,54273,54345, 54417,54489,54560,54632,54703,54774,54845,54916, 54987,55058,55129,55199,55269,55340,55410,55480, 55550,55620,55689,55759,55828,55898,55967,56036, 56105,56174,56243,56311,56380,56448,56517,56585, 56653,56721,56789,56857,56924,56992,57059,57127, 57194,57261,57328,57395,57462,57529,57595,57662, 57728,57795,57861,57927,57993,58059,58125,58191, 58256,58322,58387,58453,58518,58583,58648,58713, 58778,58843,58908,58972,59037,59101,59165,59230, 59294,59358,59422,59486,59549,59613,59677,59740, 59804,59867,59930,59993,60056,60119,60182,60245, 60308,60370,60433,60495,60558,60620,60682,60744, 60806,60868,60930,60992,61054,61115,61177,61238, 61300,61361,61422,61483,61544,61605,61666,61727, 61788,61848,61909,61969,62030,62090,62150,62211, 62271,62331,62391,62450,62510,62570,62630,62689, 62749,62808,62867,62927,62986,63045,63104,63163, 63222,63281,63340,63398,63457,63515,63574,63632, 63691,63749,63807,63865,63923,63981,64039,64097, 64155,64212,64270,64328,64385,64443,64500,64557, 64614,64672,64729,64786,64843,64900,64956,65013, 65070,65126,65183,65239,65296,65352,65409,65465 }; const png_byte png_sRGB_delta[512] = { 207,201,158,129,113,100,90,82,77,72,68,64,61,59,56,54, 52,50,49,47,46,45,43,42,41,40,39,39,38,37,36,36, 35,34,34,33,33,32,32,31,31,30,30,30,29,29,28,28, 28,27,27,27,27,26,26,26,25,25,25,25,24,24,24,24, 23,23,23,23,23,22,22,22,22,22,22,21,21,21,21,21, 21,20,20,20,20,20,20,20,20,19,19,19,19,19,19,19, 19,18,18,18,18,18,18,18,18,18,18,17,17,17,17,17, 17,17,17,17,17,17,16,16,16,16,16,16,16,16,16,16, 16,16,16,16,15,15,15,15,15,15,15,15,15,15,15,15, 15,15,15,15,14,14,14,14,14,14,14,14,14,14,14,14, 14,14,14,14,14,14,14,13,13,13,13,13,13,13,13,13, 13,13,13,13,13,13,13,13,13,13,13,13,13,13,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12, 12,12,12,12,12,12,12,12,12,12,12,12,11,11,11,11, 11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11, 11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11, 11,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10, 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10, 10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10, 10,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, 9,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,8,8,8,8,8,8,8, 8,8,8,8,8,8,8,8,8,7,7,7,7,7,7,7, 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7 }; #endif /* SIMPLIFIED READ/WRITE sRGB support */ /* SIMPLIFIED READ/WRITE SUPPORT */ #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\ defined(PNG_SIMPLIFIED_WRITE_SUPPORTED) static int png_image_free_function(png_voidp argument) { png_imagep image = png_voidcast(png_imagep, argument); png_controlp cp = image->opaque; png_control c; /* Double check that we have a png_ptr - it should be impossible to get here * without one. */ if (cp->png_ptr == NULL) return 0; /* First free any data held in the control structure. */ # ifdef PNG_STDIO_SUPPORTED if (cp->owned_file != 0) { FILE *fp = png_voidcast(FILE*, cp->png_ptr->io_ptr); cp->owned_file = 0; /* Ignore errors here. */ if (fp != NULL) { cp->png_ptr->io_ptr = NULL; (void)fclose(fp); } } # endif /* Copy the control structure so that the original, allocated, version can be * safely freed. Notice that a png_error here stops the remainder of the * cleanup, but this is probably fine because that would indicate bad memory * problems anyway. */ c = *cp; image->opaque = &c; png_free(c.png_ptr, cp); /* Then the structures, calling the correct API. */ if (c.for_write != 0) { # ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED png_destroy_write_struct(&c.png_ptr, &c.info_ptr); # else png_error(c.png_ptr, "simplified write not supported"); # endif } else { # ifdef PNG_SIMPLIFIED_READ_SUPPORTED png_destroy_read_struct(&c.png_ptr, &c.info_ptr, NULL); # else png_error(c.png_ptr, "simplified read not supported"); # endif } /* Success. */ return 1; } void PNGAPI png_image_free(png_imagep image) { /* Safely call the real function, but only if doing so is safe at this point * (if not inside an error handling context). Otherwise assume * png_safe_execute will call this API after the return. */ if (image != NULL && image->opaque != NULL && image->opaque->error_buf == NULL) { png_image_free_function(image); image->opaque = NULL; } } int /* PRIVATE */ png_image_error(png_imagep image, png_const_charp error_message) { /* Utility to log an error. */ png_safecat(image->message, (sizeof image->message), 0, error_message); image->warning_or_error |= PNG_IMAGE_ERROR; png_image_free(image); return 0; } #endif /* SIMPLIFIED READ/WRITE */ #endif /* READ || WRITE */

↑ V547 Expression 'crc == 0' is always true.

↑ V597 The compiler could delete the 'memset' function call, which is used to flush 'info_ptr' object. The RtlSecureZeroMemory() function should be used to erase the private data.

↑ V614 Uninitialized buffer 'number_buf' used. Consider checking the first actual argument of the 'png_format_number' function.

↑ V614 Uninitialized buffer 'number' used. Consider checking the first actual argument of the 'png_format_number' function.

↑ V1037 Two or more case-branches perform the same actions. Check lines: 2771, 2793

↑ V547 Expression 'items >= (~(png_alloc_size_t) 0) / size' is always false.

↑ V547 Expression 'num <= 0x80000000' is always true.

↑ V1004 The 'info_ptr_ptr' pointer was used unsafely after it was verified against nullptr. Check lines: 395, 406.

↑ V506 Pointer to local variable 'c' is stored outside the scope of this variable. Such a pointer will become invalid.

↑ V550 An odd precise comparison: d == 0. It's probably better to use a comparison with defined precision: fabs(A - B) < Epsilon.