static int read_user_chunk_callback(png_struct *png_ptr,
png_unknown_chunkp chunk)
{
png_uint_32
*my_user_chunk_data;
/* Return one of the following:
* return (-n); chunk had an error
* return (0); did not recognize
* return (n); success
*
* The unknown chunk structure contains the chunk data:
* png_byte name[5];
* png_byte *data;
* png_size_t size;
*
* Note that libpng has already taken care of the CRC handling.
*/
if (chunk->name[0] == 115 && chunk->name[1] == 84 && /* s T */
chunk->name[2] == 69 && chunk->name[3] == 82) /* E R */
{
/* Found sTER chunk */
if (chunk->size != 1)
return (-1); /* Error return */
if (chunk->data[0] != 0 && chunk->data[0] != 1)
return (-1); /* Invalid mode */
my_user_chunk_data=(png_uint_32 *) png_get_user_chunk_ptr(png_ptr);
my_user_chunk_data[0]=chunk->data[0]+1;
return (1);
}
if (chunk->name[0] != 118 || chunk->name[1] != 112 || /* v p */
chunk->name[2] != 65 || chunk->name[3] != 103) /* A g */
return (0); /* Did not recognize */
/* Found ImageMagick vpAg chunk */
if (chunk->size != 9)
return (-1); /* Error return */
my_user_chunk_data=(png_uint_32 *) png_get_user_chunk_ptr(png_ptr);
my_user_chunk_data[1]=png_get_uint_31(png_ptr, chunk->data);
my_user_chunk_data[2]=png_get_uint_31(png_ptr, chunk->data + 4);
my_user_chunk_data[3]=(png_uint_32)chunk->data[8];
return (1);
}
static int sk_read_user_chunk(png_structp png_ptr, png_unknown_chunkp chunk) {
SkImageDecoder::Peeker* peeker =
(SkImageDecoder::Peeker*)png_get_user_chunk_ptr(png_ptr);
// peek() returning true means continue decoding
return peeker->peek((const char*)chunk->name, chunk->data, chunk->size) ?
1 : -1;
}
//---------------------------------------------------------------------------
// read_chunk_callback
static int __fastcall PNG_read_chunk_callback(png_structp png_ptr,png_unknown_chunkp chunk)
{
// handle vpAg chunk (this will contain the virtual page size of the image)
// vpAg chunk can be embeded by ImageMagick -trim option etc.
// we don't care about how the chunk bit properties are being provided.
if( (chunk->name[0] == 0x76/*'v'*/ || chunk->name[0] == 0x56/*'V'*/) &&
(chunk->name[1] == 0x70/*'p'*/ || chunk->name[1] == 0x50/*'P'*/) &&
(chunk->name[2] == 0x61/*'a'*/ || chunk->name[2] == 0x41/*'A'*/) &&
(chunk->name[3] == 0x67/*'g'*/ || chunk->name[3] == 0x47/*'G'*/) && chunk->size >= 9)
{
TDeePNG * deepng =
reinterpret_cast<TDeePNG *>(png_get_user_chunk_ptr(png_ptr));
// vpAg found
/*
uint32 width
uint32 height
uchar unit
*/
// be careful because the integers are stored in network byte order
#define PNG_read_be32(a) (((unsigned long)(a)[0]<<24)+\
((unsigned long)(a)[1]<<16)+((unsigned long)(a)[2]<<8)+\
((unsigned long)(a)[3]))
unsigned long width = PNG_read_be32(chunk->data+0);
unsigned long height = PNG_read_be32(chunk->data+4);
unsigned char unit = chunk->data[8];
// set vpag information
deepng->SetVirtualPage(width, height, unit);
return 1; // chunk read success
}
return 0; // did not recognize
}
static int _loadPNGChunkHandler(png_structp png, png_unknown_chunkp chunk) {
if (strcmp((const char*) chunk->name, "gbAs") != 0) {
return 0;
}
struct GBASerializedState state;
uLongf len = sizeof(state);
uncompress((Bytef*) &state, &len, chunk->data, chunk->size);
if (!GBADeserialize(png_get_user_chunk_ptr(png), &state)) {
longjmp(png_jmpbuf(png), 1);
}
return 1;
}
static int sk_read_user_chunk(png_structp png_ptr, png_unknown_chunkp chunk) {
SkPngChunkReader* chunkReader = (SkPngChunkReader*)png_get_user_chunk_ptr(png_ptr);
// readChunk() returning true means continue decoding
return chunkReader->readChunk((const char*)chunk->name, chunk->data, chunk->size) ? 1 : -1;
}
