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304 lines
9.4 KiB
304 lines
9.4 KiB
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/* png.c - location for general purpose libpng functions |
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* |
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* libpng 1.0.1 |
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* For conditions of distribution and use, see copyright notice in png.h |
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* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc. |
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* Copyright (c) 1996, 1997 Andreas Dilger |
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* Copyright (c) 1998, Glenn Randers-Pehrson |
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* March 9, 1998 |
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*/ |
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#define PNG_INTERNAL |
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#define PNG_NO_EXTERN |
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#include "png.h" |
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/* Version information for C files. This had better match the version |
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* string defined in png.h. |
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*/ |
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char png_libpng_ver[6] = "1.0.1"; |
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/* Place to hold the signature string for a PNG file. */ |
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png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10}; |
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/* Constant strings for known chunk types. If you need to add a chunk, |
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* add a string holding the name here. If you want to make the code |
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* portable to EBCDIC machines, use ASCII numbers, not characters. |
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*/ |
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png_byte FARDATA png_IHDR[5] = { 73, 72, 68, 82, '\0'}; |
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png_byte FARDATA png_IDAT[5] = { 73, 68, 65, 84, '\0'}; |
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png_byte FARDATA png_IEND[5] = { 73, 69, 78, 68, '\0'}; |
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png_byte FARDATA png_PLTE[5] = { 80, 76, 84, 69, '\0'}; |
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png_byte FARDATA png_bKGD[5] = { 98, 75, 71, 68, '\0'}; |
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png_byte FARDATA png_cHRM[5] = { 99, 72, 82, 77, '\0'}; |
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png_byte FARDATA png_gAMA[5] = {103, 65, 77, 65, '\0'}; |
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png_byte FARDATA png_hIST[5] = {104, 73, 83, 84, '\0'}; |
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png_byte FARDATA png_oFFs[5] = {111, 70, 70, 115, '\0'}; |
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png_byte FARDATA png_pCAL[5] = {112, 67, 65, 76, '\0'}; |
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png_byte FARDATA png_pHYs[5] = {112, 72, 89, 115, '\0'}; |
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png_byte FARDATA png_sBIT[5] = {115, 66, 73, 84, '\0'}; |
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png_byte FARDATA png_sRGB[5] = {115, 82, 71, 66, '\0'}; |
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png_byte FARDATA png_tEXt[5] = {116, 69, 88, 116, '\0'}; |
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png_byte FARDATA png_tIME[5] = {116, 73, 77, 69, '\0'}; |
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png_byte FARDATA png_tRNS[5] = {116, 82, 78, 83, '\0'}; |
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png_byte FARDATA png_zTXt[5] = {122, 84, 88, 116, '\0'}; |
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/* arrays to facilitate easy interlacing - use pass (0 - 6) as index */ |
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/* start of interlace block */ |
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int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0}; |
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/* offset to next interlace block */ |
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int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1}; |
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/* start of interlace block in the y direction */ |
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int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1}; |
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/* offset to next interlace block in the y direction */ |
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int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2}; |
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/* Width of interlace block. This is not currently used - if you need |
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* it, uncomment it here and in png.h |
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int FARDATA png_pass_width[] = {8, 4, 4, 2, 2, 1, 1}; |
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*/ |
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/* Height of interlace block. This is not currently used - if you need |
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* it, uncomment it here and in png.h |
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int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1}; |
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*/ |
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/* Mask to determine which pixels are valid in a pass */ |
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int FARDATA png_pass_mask[] = {0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff}; |
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/* Mask to determine which pixels to overwrite while displaying */ |
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int FARDATA png_pass_dsp_mask[] = {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff}; |
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/* Tells libpng that we have already handled the first "num_bytes" bytes |
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* of the PNG file signature. If the PNG data is embedded into another |
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* stream we can set num_bytes = 8 so that libpng will not attempt to read |
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* or write any of the magic bytes before it starts on the IHDR. |
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*/ |
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void |
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png_set_sig_bytes(png_structp png_ptr, int num_bytes) |
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{ |
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png_debug(1, "in png_set_sig_bytes\n"); |
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if (num_bytes > 8) |
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png_error(png_ptr, "Too many bytes for PNG signature."); |
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png_ptr->sig_bytes = num_bytes < 0 ? 0 : num_bytes; |
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} |
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/* Checks whether the supplied bytes match the PNG signature. We allow |
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* checking less than the full 8-byte signature so that those apps that |
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* already read the first few bytes of a file to determine the file type |
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* can simply check the remaining bytes for extra assurance. Returns |
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* an integer less than, equal to, or greater than zero if sig is found, |
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* respectively, to be less than, to match, or be greater than the correct |
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* PNG signature (this is the same behaviour as strcmp, memcmp, etc). |
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*/ |
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int |
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png_sig_cmp(png_bytep sig, png_size_t start, png_size_t num_to_check) |
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{ |
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if (num_to_check > 8) |
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num_to_check = 8; |
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else if (num_to_check < 1) |
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return (0); |
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if (start > 7) |
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return (0); |
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if (start + num_to_check > 8) |
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num_to_check = 8 - start; |
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return ((int)(png_memcmp(&sig[start], &png_sig[start], num_to_check))); |
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} |
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/* (Obsolete) function to check signature bytes. It does not allow one |
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* to check a partial signature. This function will be removed in the |
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* future - use png_sig_cmp(). |
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*/ |
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int |
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png_check_sig(png_bytep sig, int num) |
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{ |
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return ((int)!png_sig_cmp(sig, (png_size_t)0, (png_size_t)num)); |
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} |
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/* Function to allocate memory for zlib. */ |
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voidpf |
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png_zalloc(voidpf png_ptr, uInt items, uInt size) |
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{ |
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png_voidp ptr; |
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png_uint_32 num_bytes; |
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num_bytes = (png_uint_32)items * size; |
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ptr = (png_voidp)png_malloc((png_structp)png_ptr, num_bytes); |
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if (num_bytes > (png_uint_32)0x8000) |
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{ |
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png_memset(ptr, 0, (png_size_t)0x8000L); |
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png_memset((png_bytep)ptr + (png_size_t)0x8000L, 0, |
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(png_size_t)(num_bytes - (png_uint_32)0x8000L)); |
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} |
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else |
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{ |
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png_memset(ptr, 0, (png_size_t)num_bytes); |
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} |
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return ((voidpf)ptr); |
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} |
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/* function to free memory for zlib */ |
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void |
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png_zfree(voidpf png_ptr, voidpf ptr) |
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{ |
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png_free((png_structp)png_ptr, (png_voidp)ptr); |
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} |
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/* Reset the CRC variable to 32 bits of 1's. Care must be taken |
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* in case CRC is > 32 bits to leave the top bits 0. |
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*/ |
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void |
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png_reset_crc(png_structp png_ptr) |
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{ |
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png_ptr->crc = crc32(0, Z_NULL, 0); |
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} |
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/* Calculate the CRC over a section of data. We can only pass as |
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* much data to this routine as the largest single buffer size. We |
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* also check that this data will actually be used before going to the |
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* trouble of calculating it. |
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*/ |
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void |
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png_calculate_crc(png_structp png_ptr, png_bytep ptr, png_size_t length) |
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{ |
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int need_crc = 1; |
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if (png_ptr->chunk_name[0] & 0x20) /* ancillary */ |
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{ |
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if ((png_ptr->flags & PNG_FLAG_CRC_ANCILLARY_MASK) == |
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(PNG_FLAG_CRC_ANCILLARY_USE | PNG_FLAG_CRC_ANCILLARY_NOWARN)) |
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need_crc = 0; |
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} |
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else /* critical */ |
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{ |
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if (png_ptr->flags & PNG_FLAG_CRC_CRITICAL_IGNORE) |
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need_crc = 0; |
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} |
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if (need_crc) |
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png_ptr->crc = crc32(png_ptr->crc, ptr, (uInt)length); |
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} |
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/* Allocate the memory for an info_struct for the application. We don't |
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* really need the png_ptr, but it could potentially be useful in the |
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* future. This should be used in favour of malloc(sizeof(png_info)) |
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* and png_info_init() so that applications that want to use a shared |
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* libpng don't have to be recompiled if png_info changes size. |
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*/ |
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png_infop |
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png_create_info_struct(png_structp png_ptr) |
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{ |
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png_infop info_ptr; |
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png_debug(1, "in png_create_info_struct\n"); |
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if(png_ptr == NULL) return (NULL); |
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if ((info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO)) != NULL) |
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{ |
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png_info_init(info_ptr); |
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} |
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return (info_ptr); |
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} |
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/* This function frees the memory associated with a single info struct. |
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* Normally, one would use either png_destroy_read_struct() or |
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* png_destroy_write_struct() to free an info struct, but this may be |
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* useful for some applications. |
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*/ |
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void |
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png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr) |
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{ |
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png_infop info_ptr = NULL; |
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png_debug(1, "in png_destroy_info_struct\n"); |
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if (info_ptr_ptr != NULL) |
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info_ptr = *info_ptr_ptr; |
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if (info_ptr != NULL) |
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{ |
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png_info_destroy(png_ptr, info_ptr); |
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png_destroy_struct((png_voidp)info_ptr); |
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*info_ptr_ptr = (png_infop)NULL; |
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} |
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} |
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/* Initialize the info structure. This is now an internal function (0.89) |
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* and applications using it are urged to use png_create_info_struct() |
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* instead. |
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*/ |
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void |
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png_info_init(png_infop info_ptr) |
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{ |
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png_debug(1, "in png_info_init\n"); |
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/* set everything to 0 */ |
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png_memset(info_ptr, 0, sizeof (png_info)); |
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} |
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/* This is an internal routine to free any memory that the info struct is |
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* pointing to before re-using it or freeing the struct itself. Recall |
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* that png_free() checks for NULL pointers for us. |
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*/ |
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void |
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png_info_destroy(png_structp png_ptr, png_infop info_ptr) |
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{ |
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#if defined(PNG_READ_tEXt_SUPPORTED) || defined(PNG_READ_zTXt_SUPPORTED) |
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int i; |
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png_debug(1, "in png_info_destroy\n"); |
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if (info_ptr->text != NULL) |
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{ |
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for (i = 0; i < info_ptr->num_text; i++) |
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{ |
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png_free(png_ptr, info_ptr->text[i].key); |
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} |
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png_free(png_ptr, info_ptr->text); |
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} |
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#endif |
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#if defined(PNG_READ_pCAL_SUPPORTED) |
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png_free(png_ptr, info_ptr->pcal_purpose); |
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png_free(png_ptr, info_ptr->pcal_units); |
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if (info_ptr->pcal_params != NULL) |
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{ |
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for (i = 0; i < (int)info_ptr->pcal_nparams; i++) |
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{ |
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png_free(png_ptr, info_ptr->pcal_params[i]); |
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} |
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png_free(png_ptr, info_ptr->pcal_params); |
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} |
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#endif |
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png_info_init(info_ptr); |
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} |
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/* This function returns a pointer to the io_ptr associated with the user |
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* functions. The application should free any memory associated with this |
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* pointer before png_write_destroy() or png_read_destroy() are called. |
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*/ |
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png_voidp |
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png_get_io_ptr(png_structp png_ptr) |
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{ |
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return (png_ptr->io_ptr); |
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} |
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#if !defined(PNG_NO_STDIO) |
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/* Initialize the default input/output functions for the PNG file. If you |
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* use your own read or write routines, you can call either png_set_read_fn() |
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* or png_set_write_fn() instead of png_init_io(). |
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*/ |
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void |
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png_init_io(png_structp png_ptr, FILE *fp) |
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{ |
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png_debug(1, "in png_init_io\n"); |
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png_ptr->io_ptr = (png_voidp)fp; |
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} |
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#endif
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