www.pudn.com > Image_png.rar > png.c
/* png.c - location for general purpose libpng functions
*
* libpng 1.0.1
* For conditions of distribution and use, see copyright notice in png.h
* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
* Copyright (c) 1996, 1997 Andreas Dilger
* Copyright (c) 1998, Glenn Randers-Pehrson
* March 15, 1998
*/
#define PNG_INTERNAL
#define PNG_NO_EXTERN
#include "png.h"
/* Version information for C files. This had better match the version
* string defined in png.h.
*/
char png_libpng_ver[12] = "1.0.1";
/* Place to hold the signature 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[5] = { 73, 72, 68, 82, '\0'};
png_byte FARDATA png_IDAT[5] = { 73, 68, 65, 84, '\0'};
png_byte FARDATA png_IEND[5] = { 73, 69, 78, 68, '\0'};
png_byte FARDATA png_PLTE[5] = { 80, 76, 84, 69, '\0'};
png_byte FARDATA png_bKGD[5] = { 98, 75, 71, 68, '\0'};
png_byte FARDATA png_cHRM[5] = { 99, 72, 82, 77, '\0'};
png_byte FARDATA png_gAMA[5] = {103, 65, 77, 65, '\0'};
png_byte FARDATA png_hIST[5] = {104, 73, 83, 84, '\0'};
png_byte FARDATA png_oFFs[5] = {111, 70, 70, 115, '\0'};
png_byte FARDATA png_pCAL[5] = {112, 67, 65, 76, '\0'};
png_byte FARDATA png_pHYs[5] = {112, 72, 89, 115, '\0'};
png_byte FARDATA png_sBIT[5] = {115, 66, 73, 84, '\0'};
png_byte FARDATA png_sRGB[5] = {115, 82, 71, 66, '\0'};
png_byte FARDATA png_tEXt[5] = {116, 69, 88, 116, '\0'};
png_byte FARDATA png_tIME[5] = {116, 73, 77, 69, '\0'};
png_byte FARDATA png_tRNS[5] = {116, 82, 78, 83, '\0'};
png_byte FARDATA png_zTXt[5] = {122, 84, 88, 116, '\0'};
/* 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};
/* 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.
*/
void
png_set_sig_bytes(png_structp png_ptr, int num_bytes)
{
png_debug(1, "in png_set_sig_bytes\n");
if (num_bytes > 8)
png_error(png_ptr, "Too many bytes for PNG signature.");
png_ptr->sig_bytes = num_bytes < 0 ? 0 : num_bytes;
}
/* 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 behaviour as strcmp, memcmp, etc).
*/
int
png_sig_cmp(png_bytep sig, png_size_t start, png_size_t num_to_check)
{
if (num_to_check > 8)
num_to_check = 8;
else if (num_to_check < 1)
return (0);
if (start > 7)
return (0);
if (start + num_to_check > 8)
num_to_check = 8 - start;
return ((int)(png_memcmp(&sig[start], &png_sig[start], num_to_check)));
}
/* (Obsolete) function to check signature bytes. It does not allow one
* to check a partial signature. This function will be removed in the
* future - use png_sig_cmp().
*/
int
png_check_sig(png_bytep sig, int num)
{
return ((int)!png_sig_cmp(sig, (png_size_t)0, (png_size_t)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;
num_bytes = (png_uint_32)items * size;
ptr = (png_voidp)png_malloc((png_structp)png_ptr, num_bytes);
if (num_bytes > (png_uint_32)0x8000)
{
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_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)
{
png_ptr->crc = 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
png_calculate_crc(png_structp png_ptr, png_bytep ptr, png_size_t length)
{
int need_crc = 1;
if (png_ptr->chunk_name[0] & 0x20) /* ancillary */
{
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)
need_crc = 0;
}
if (need_crc)
png_ptr->crc = crc32(png_ptr->crc, ptr, (uInt)length);
}
/* Allocate the memory for an info_struct for the application. We don't
* really need the png_ptr, but it could potentially be useful in the
* future. This should be used in favour of malloc(sizeof(png_info))
* and png_info_init() so that applications that want to use a shared
* libpng don't have to be recompiled if png_info changes size.
*/
png_infop
png_create_info_struct(png_structp png_ptr)
{
png_infop info_ptr;
png_debug(1, "in png_create_info_struct\n");
if(png_ptr == NULL) return (NULL);
if ((info_ptr = (png_infop)png_create_struct(PNG_STRUCT_INFO)) != NULL)
{
png_info_init(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.
*/
void
png_destroy_info_struct(png_structp png_ptr, png_infopp info_ptr_ptr)
{
png_infop info_ptr = NULL;
png_debug(1, "in png_destroy_info_struct\n");
if (info_ptr_ptr != NULL)
info_ptr = *info_ptr_ptr;
if (info_ptr != NULL)
{
png_info_destroy(png_ptr, info_ptr);
png_destroy_struct((png_voidp)info_ptr);
*info_ptr_ptr = (png_infop)NULL;
}
}
/* 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.
*/
void
png_info_init(png_infop info_ptr)
{
png_debug(1, "in png_info_init\n");
/* set everything to 0 */
png_memset(info_ptr, 0, sizeof (png_info));
}
/* This is an internal routine to free any memory that the info struct is
* pointing to before re-using it or freeing the struct itself. Recall
* that png_free() checks for NULL pointers for us.
*/
void
png_info_destroy(png_structp png_ptr, png_infop info_ptr)
{
#if defined(PNG_READ_tEXt_SUPPORTED) || defined(PNG_READ_zTXt_SUPPORTED)
int i;
png_debug(1, "in png_info_destroy\n");
if (info_ptr->text != NULL)
{
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);
}
#endif
#if defined(PNG_READ_pCAL_SUPPORTED)
png_free(png_ptr, info_ptr->pcal_purpose);
png_free(png_ptr, info_ptr->pcal_units);
if (info_ptr->pcal_params != NULL)
{
for (i = 0; i < (int)info_ptr->pcal_nparams; i++)
{
png_free(png_ptr, info_ptr->pcal_params[i]);
}
png_free(png_ptr, info_ptr->pcal_params);
}
#endif
png_info_init(info_ptr);
}
/* 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
png_get_io_ptr(png_structp png_ptr)
{
return (png_ptr->io_ptr);
}
#if !defined(PNG_NO_STDIO)
/* 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().
*/
void
png_init_io(png_structp png_ptr, FILE *fp)
{
png_debug(1, "in png_init_io\n");
png_ptr->io_ptr = (png_voidp)fp;
}
#endif