204 lines
5.8 KiB
C
204 lines
5.8 KiB
C
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/* png.c - location for general purpose png functions
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libpng 1.0 beta 2 - version 0.81
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For conditions of distribution and use, see copyright notice in png.h
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Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc.
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August 24, 1995
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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 better match the version
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string defined in png.h */
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char png_libpng_ver[] = "0.81";
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/* place to hold the signiture string for a png file. */
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png_byte 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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png_byte png_IHDR[4] = { 73, 72, 68, 82};
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png_byte png_IDAT[4] = { 73, 68, 65, 84};
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png_byte png_IEND[4] = { 73, 69, 78, 68};
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png_byte png_PLTE[4] = { 80, 76, 84, 69};
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#if defined(PNG_READ_gAMA_SUPPORTED) || defined(PNG_WRITE_gAMA_SUPPORTED)
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png_byte png_gAMA[4] = {103, 65, 77, 65};
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#endif
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#if defined(PNG_READ_sBIT_SUPPORTED) || defined(PNG_WRITE_sBIT_SUPPORTED)
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png_byte png_sBIT[4] = {115, 66, 73, 84};
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#endif
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#if defined(PNG_READ_cHRM_SUPPORTED) || defined(PNG_WRITE_cHRM_SUPPORTED)
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png_byte png_cHRM[4] = { 99, 72, 82, 77};
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#endif
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#if defined(PNG_READ_tRNS_SUPPORTED) || defined(PNG_WRITE_tRNS_SUPPORTED)
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png_byte png_tRNS[4] = {116, 82, 78, 83};
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#endif
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#if defined(PNG_READ_bKGD_SUPPORTED) || defined(PNG_WRITE_bKGD_SUPPORTED)
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png_byte png_bKGD[4] = { 98, 75, 71, 68};
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#endif
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#if defined(PNG_READ_hIST_SUPPORTED) || defined(PNG_WRITE_hIST_SUPPORTED)
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png_byte png_hIST[4] = {104, 73, 83, 84};
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#endif
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#if defined(PNG_READ_tEXt_SUPPORTED) || defined(PNG_WRITE_tEXt_SUPPORTED)
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png_byte png_tEXt[4] = {116, 69, 88, 116};
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#endif
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#if defined(PNG_READ_zTXt_SUPPORTED) || defined(PNG_WRITE_zTXt_SUPPORTED)
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png_byte png_zTXt[4] = {122, 84, 88, 116};
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#endif
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#if defined(PNG_READ_pHYs_SUPPORTED) || defined(PNG_WRITE_pHYs_SUPPORTED)
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png_byte png_pHYs[4] = {112, 72, 89, 115};
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#endif
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#if defined(PNG_READ_oFFs_SUPPORTED) || defined(PNG_WRITE_oFFs_SUPPORTED)
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png_byte png_oFFs[4] = {111, 70, 70, 115};
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#endif
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#if defined(PNG_READ_tIME_SUPPORTED) || defined(PNG_WRITE_tIME_SUPPORTED)
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png_byte png_tIME[4] = {116, 73, 77, 69};
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#endif
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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 png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
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/* offset to next interlace block */
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int 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 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 png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
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/* width of interlace block */
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/* this is not currently used - if you need it, uncomment it here and
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in png.h
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int png_pass_width[] = {8, 4, 4, 2, 2, 1, 1};
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*/
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/* height of interlace block */
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/* this is not currently used - if you need it, uncomment it here and
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in png.h
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int png_pass_height[] = {8, 8, 4, 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 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 png_pass_dsp_mask[] = {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff};
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int
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png_check_sig(png_byte *sig, int num)
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{
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if (num > 8)
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num = 8;
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if (num < 1)
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return 0;
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return (!memcmp(sig, png_sig, 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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return ((voidpf)png_large_malloc((png_struct FAR *)png_ptr,
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(png_uint_32)items * (png_uint_32)size));
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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_large_free((png_struct FAR *)png_ptr, (voidpf)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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void
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png_reset_crc(png_struct *png_ptr)
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{
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/* set crc to all 1's */
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png_ptr->crc = 0xffffffffL;
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}
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/* Note: the crc code below was copied from the sample code in the
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PNG spec, with appropriate modifications made to ensure the
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variables are large enough */
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/* table of crc's of all 8-bit messages. If you wish to png_malloc this
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table, turn this into a pointer, and png_malloc it in make_crc_table().
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You may then want to hook it into png_struct and free it with the
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destroy functions. */
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static png_uint_32 crc_table[256];
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/* Flag: has the table been computed? Initially false. */
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static int crc_table_computed = 0;
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/* make the table for a fast crc */
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static void
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make_crc_table(void)
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{
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png_uint_32 c;
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int n, k;
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for (n = 0; n < 256; n++)
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{
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c = (png_uint_32)n;
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for (k = 0; k < 8; k++)
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c = c & 1 ? 0xedb88320L ^ (c >> 1) : c >> 1;
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crc_table[n] = c;
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}
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crc_table_computed = 1;
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}
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/* update a running crc with the bytes buf[0..len-1]--the crc should be
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initialized to all 1's, and the transmitted value is the 1's complement
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of the final running crc. */
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static png_uint_32
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update_crc(png_uint_32 crc, png_bytef *buf, png_uint_32 len)
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{
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png_uint_32 c;
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png_bytef *p;
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png_uint_32 n;
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c = crc;
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p = buf;
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n = len;
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if (!crc_table_computed)
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{
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make_crc_table();
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}
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if (n > 0) do
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{
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c = crc_table[(png_byte)((c ^ (*p++)) & 0xff)] ^ (c >> 8);
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} while (--n);
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return c;
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}
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/* calculate the crc over a section of data. Note that while we
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are passing in a 32 bit value for length, on 16 bit machines, you
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would need to use huge pointers to access all that data. If you
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need this, put huge here and above. */
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void
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png_calculate_crc(png_struct *png_ptr, png_bytef *ptr,
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png_uint_32 length)
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{
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png_ptr->crc = update_crc(png_ptr->crc, ptr, length);
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}
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void
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png_info_init(png_info *info)
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{
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/* set everything to 0 */
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memset(info, 0, sizeof (png_info));
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}
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