| |
| /* png.c - location for general purpose png functions |
| |
| libpng 1.0 beta 3 - version 0.89 |
| For conditions of distribution and use, see copyright notice in png.h |
| Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc. |
| May 25, 1996 |
| */ |
| |
| #define PNG_INTERNAL |
| #define PNG_NO_EXTERN |
| #include "png.h" |
| |
| /* version information for c files. This better match the version |
| string defined in png.h */ |
| char png_libpng_ver[] = "0.89"; |
| |
| /* place to hold the signiture string for a png file. */ |
| png_byte FARDATA png_sig[8] = {137, 80, 78, 71, 13, 10, 26, 10}; |
| |
| /* constant strings for known chunk types. If you need to add a chunk, |
| add a string holding the name here. If you want to make the code |
| portable to EBCDIC machines, use ASCII numbers, not characters. */ |
| png_byte FARDATA png_IHDR[4] = { 73, 72, 68, 82}; |
| png_byte FARDATA png_IDAT[4] = { 73, 68, 65, 84}; |
| png_byte FARDATA png_IEND[4] = { 73, 69, 78, 68}; |
| png_byte FARDATA png_PLTE[4] = { 80, 76, 84, 69}; |
| png_byte FARDATA png_gAMA[4] = {103, 65, 77, 65}; |
| png_byte FARDATA png_sBIT[4] = {115, 66, 73, 84}; |
| png_byte FARDATA png_cHRM[4] = { 99, 72, 82, 77}; |
| png_byte FARDATA png_tRNS[4] = {116, 82, 78, 83}; |
| png_byte FARDATA png_bKGD[4] = { 98, 75, 71, 68}; |
| png_byte FARDATA png_hIST[4] = {104, 73, 83, 84}; |
| png_byte FARDATA png_tEXt[4] = {116, 69, 88, 116}; |
| png_byte FARDATA png_zTXt[4] = {122, 84, 88, 116}; |
| png_byte FARDATA png_pHYs[4] = {112, 72, 89, 115}; |
| png_byte FARDATA png_oFFs[4] = {111, 70, 70, 115}; |
| png_byte FARDATA png_tIME[4] = {116, 73, 77, 69}; |
| |
| /* arrays to facilitate easy interlacing - use pass (0 - 6) as index */ |
| |
| /* start of interlace block */ |
| int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0}; |
| |
| /* offset to next interlace block */ |
| int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1}; |
| |
| /* start of interlace block in the y direction */ |
| int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1}; |
| |
| /* offset to next interlace block in the y direction */ |
| int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2}; |
| |
| /* width of interlace block */ |
| /* this is not currently used - if you need it, uncomment it here and |
| in png.h |
| int FARDATA png_pass_width[] = {8, 4, 4, 2, 2, 1, 1}; |
| */ |
| |
| /* height of interlace block */ |
| /* this is not currently used - if you need it, uncomment it here and |
| in png.h |
| int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1}; |
| */ |
| |
| /* mask to determine which pixels are valid in a pass */ |
| int FARDATA png_pass_mask[] = {0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff}; |
| |
| /* mask to determine which pixels to overwrite while displaying */ |
| int FARDATA png_pass_dsp_mask[] = {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff}; |
| |
| |
| int |
| png_check_sig(png_bytep sig, int num) |
| { |
| if (num > 8) |
| num = 8; |
| if (num < 1) |
| return 0; |
| |
| return (!png_memcmp(sig, png_sig, num)); |
| } |
| |
| /* Function to allocate memory for zlib. */ |
| voidpf |
| png_zalloc(voidpf png_ptr, uInt items, uInt size) |
| { |
| png_voidp ptr; |
| png_uint_32 num_bytes; |
| |
| ptr = png_large_malloc((png_structp)png_ptr, |
| (png_uint_32)items * (png_uint_32)size); |
| num_bytes = (png_uint_32)items * (png_uint_32)size; |
| if (num_bytes > (png_uint_32)0x7fff) |
| { |
| png_memset(ptr, 0, (png_size_t)0x8000L); |
| png_memset((png_bytep)ptr + (png_size_t)0x8000L, 0, |
| (png_size_t)(num_bytes - (png_uint_32)0x8000L)); |
| } |
| else |
| { |
| png_memset(ptr, 0, (png_size_t)num_bytes); |
| } |
| return (voidpf)(ptr); |
| } |
| |
| /* function to free memory for zlib */ |
| void |
| png_zfree(voidpf png_ptr, voidpf ptr) |
| { |
| png_large_free((png_structp)png_ptr, (png_voidp)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 |
| png_reset_crc(png_structp png_ptr) |
| { |
| /* set crc to all 1's */ |
| png_ptr->crc = 0xffffffffL; |
| } |
| |
| /* Note: the crc code below was copied from the sample code in the |
| PNG spec, with appropriate modifications made to ensure the |
| variables are large enough */ |
| |
| /* table of crc's of all 8-bit messages. If you wish to png_malloc this |
| table, turn this into a pointer, and png_malloc it in make_crc_table(). |
| You may then want to hook it into png_struct and free it with the |
| destroy functions. */ |
| static png_uint_32 crc_table[256]; |
| |
| /* Flag: has the table been computed? Initially false. */ |
| static int crc_table_computed = 0; |
| |
| /* make the table for a fast crc */ |
| static void |
| make_crc_table(void) |
| { |
| png_uint_32 c; |
| int n, k; |
| |
| for (n = 0; n < 256; n++) |
| { |
| c = (png_uint_32)n; |
| for (k = 0; k < 8; k++) |
| c = c & 1 ? 0xedb88320L ^ (c >> 1) : c >> 1; |
| crc_table[n] = c; |
| } |
| crc_table_computed = 1; |
| } |
| |
| /* update a running crc with the bytes buf[0..len-1]--the crc should be |
| initialized to all 1's, and the transmitted value is the 1's complement |
| of the final running crc. */ |
| static png_uint_32 |
| update_crc(png_uint_32 crc, png_bytep buf, png_uint_32 len) |
| { |
| png_uint_32 c; |
| png_bytep p; |
| png_uint_32 n; |
| |
| c = crc; |
| p = buf; |
| n = len; |
| |
| if (!crc_table_computed) |
| { |
| make_crc_table(); |
| } |
| |
| if (n > 0) do |
| { |
| c = crc_table[(png_byte)((c ^ (*p++)) & 0xff)] ^ (c >> 8); |
| } while (--n); |
| |
| return c; |
| } |
| |
| /* calculate the crc over a section of data. Note that while we |
| are passing in a 32 bit value for length, on 16 bit machines, you |
| would need to use huge pointers to access all that data. If you |
| need this, put huge here and above. */ |
| void |
| png_calculate_crc(png_structp png_ptr, png_bytep ptr, |
| png_uint_32 length) |
| { |
| png_ptr->crc = update_crc(png_ptr->crc, ptr, length); |
| } |
| |
| png_infop |
| png_create_info_struct(png_structp png_ptr) |
| { |
| png_infop info_ptr; |
| |
| if ((info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO)) != NULL) |
| { |
| png_memset(info_ptr, 0, sizeof(png_info)); |
| png_ptr->do_free |= PNG_FREE_INFO; |
| } |
| |
| return info_ptr; |
| } |
| |
| void |
| png_info_init(png_infop info) |
| { |
| /* set everything to 0 */ |
| png_memset(info, 0, sizeof (png_info)); |
| } |
| |
| /* 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 and png_read_destroy are called. */ |
| png_voidp |
| png_get_io_ptr(png_structp png_ptr) |
| { |
| return png_ptr->io_ptr; |
| } |
| |
| /* Initialize the default input/output functions for the png file. If you |
| change the read, or write routines, you can call either png_set_read_fn() |
| or png_set_write_fn() instead of png_init_io(). */ |
| void |
| png_init_io(png_structp png_ptr, FILE *fp) |
| { |
| png_ptr->io_ptr = (png_voidp)fp; |
| } |