void PngChunk::decode(Image* pImage,
const byte* pData,
long size)
{
assert(pImage != 0);
assert(pData != 0);
// look for a tEXt chunk
long index = 8;
index += getLong(&pData[index], bigEndian) + PNG_CHUNK_HEADER_SIZE;
while(index < size-PNG_CHUNK_HEADER_SIZE)
{
while (index < size-PNG_CHUNK_HEADER_SIZE &&
strncmp((char*)PNG_CHUNK_TYPE(pData, index), "tEXt", 4) &&
strncmp((char*)PNG_CHUNK_TYPE(pData, index), "zTXt", 4) &&
strncmp((char*)PNG_CHUNK_TYPE(pData, index), "iTXt", 4))
{
if (!strncmp((char*)PNG_CHUNK_TYPE(pData, index), "IEND", 4))
throw Error(14);
index += getLong(&pData[index], bigEndian) + PNG_CHUNK_HEADER_SIZE;
}
if (index < size-PNG_CHUNK_HEADER_SIZE)
{
// we found a tEXt, zTXt, or iTXt field
// get the key, it's a null terminated string at the chunk start
const byte *key = &PNG_CHUNK_DATA(pData, index, 0);
int keysize=0;
for ( ; key[keysize] != 0 ; keysize++)
{
// look if we reached the end of the file (it might be corrupted)
if (8+index+keysize >= size)
throw Error(14);
}
DataBuf arr = parsePngChunk(pData, size, index, keysize);
#ifdef DEBUG
std::cerr << "Exiv2::PngChunk::decode: Found PNG chunk: "
<< std::string((const char*)key) << " :: "
<< std::string((const char*)arr.pData_, 32) << "\n";
#endif
parseChunkContent(pImage, key, arr);
index += getLong(&pData[index], bigEndian) + PNG_CHUNK_HEADER_SIZE;
}
}
} // PngChunk::decode
DataBuf PngChunk::parsePngChunk(const byte* pData, long size, long& index, int keysize)
{
DataBuf arr;
if(!strncmp((char*)PNG_CHUNK_TYPE(pData, index), "zTXt", 4))
{
// Extract a deflate compressed Latin-1 text chunk
#ifdef DEBUG
std::cerr << "Exiv2::PngChunk::parsePngChunk: We found a zTXt field\n";
#endif
// we get the compression method after the key
const byte* compressionMethod = &PNG_CHUNK_DATA(pData, index, keysize+1);
if ( *compressionMethod != 0x00 )
{
// then it isn't zlib compressed and we are sunk
#ifdef DEBUG
std::cerr << "Exiv2::PngChunk::parsePngChunk: Non-standard zTXt compression method.\n";
#endif
throw Error(14);
}
// compressed string after the compression technique spec
const byte* compressedText = &PNG_CHUNK_DATA(pData, index, keysize+2);
unsigned int compressedTextSize = getLong(&pData[index], bigEndian)-keysize-2;
// security check, also considering overflow wraparound from the addition --
// we may endup with a /smaller/ index if we wrap all the way around
long firstIndex = (long)(compressedText - pData);
long onePastLastIndex = firstIndex + compressedTextSize;
if ( onePastLastIndex > size || onePastLastIndex <= firstIndex)
throw Error(14);
zlibUncompress(compressedText, compressedTextSize, arr);
}
else if (!strncmp((char*)PNG_CHUNK_TYPE(pData, index), "tEXt", 4))
{
// Extract a non-compressed Latin-1 text chunk
#ifdef DEBUG
std::cerr << "Exiv2::PngChunk::parsePngChunk: We found a tEXt field\n";
#endif
// the text comes after the key, but isn't null terminated
const byte* text = &PNG_CHUNK_DATA(pData, index, keysize+1);
long textsize = getLong(&pData[index], bigEndian)-keysize-1;
// security check, also considering overflow wraparound from the addition --
// we may endup with a /smaller/ index if we wrap all the way around
long firstIndex = (long)(text - pData);
long onePastLastIndex = firstIndex + textsize;
if ( onePastLastIndex > size || onePastLastIndex <= firstIndex)
throw Error(14);
arr.alloc(textsize);
arr = DataBuf(text, textsize);
}
else if(!strncmp((char*)PNG_CHUNK_TYPE(pData, index), "iTXt", 4))
{
// Extract a deflate compressed or uncompressed UTF-8 text chunk
// we get the compression flag after the key
const byte* compressionFlag = &PNG_CHUNK_DATA(pData, index, keysize+1);
// we get the compression method after the compression flag
const byte* compressionMethod = &PNG_CHUNK_DATA(pData, index, keysize+1);
// language description string after the compression technique spec
const byte* languageText = &PNG_CHUNK_DATA(pData, index, keysize+1);
unsigned int languageTextSize = getLong(&pData[index], bigEndian)-keysize-1;
// translated keyword string after the language description
const byte* translatedKeyText = &PNG_CHUNK_DATA(pData, index, keysize+1);
unsigned int translatedKeyTextSize = getLong(&pData[index], bigEndian)-keysize-1;
if ( *compressionFlag == 0x00 )
{
// then it's an uncompressed iTXt chunk
#ifdef DEBUG
std::cerr << "Exiv2::PngChunk::parsePngChunk: We found an uncompressed iTXt field\n";
#endif
// the text comes after the translated keyword, but isn't null terminated
const byte* text = &PNG_CHUNK_DATA(pData, index, keysize+1);
long textsize = getLong(&pData[index], bigEndian)-keysize-1;
// security check, also considering overflow wraparound from the addition --
// we may endup with a /smaller/ index if we wrap all the way around
long firstIndex = (long)(text - pData);
long onePastLastIndex = firstIndex + textsize;
if ( onePastLastIndex > size || onePastLastIndex <= firstIndex)
throw Error(14);
arr.alloc(textsize);
arr = DataBuf(text, textsize);
}
else if ( *compressionMethod == 0x00 )
{
// then it's a zlib compressed iTXt chunk
#ifdef DEBUG
std::cerr << "Exiv2::PngChunk::parsePngChunk: We found a zlib compressed iTXt field\n";
#endif
// the compressed text comes after the translated keyword, but isn't null terminated
const byte* compressedText = &PNG_CHUNK_DATA(pData, index, keysize+1);
long compressedTextSize = getLong(&pData[index], bigEndian)-keysize-1;
// security check, also considering overflow wraparound from the addition --
// we may endup with a /smaller/ index if we wrap all the way around
long firstIndex = (long)(compressedText - pData);
long onePastLastIndex = firstIndex + compressedTextSize;
if ( onePastLastIndex > size || onePastLastIndex <= firstIndex)
throw Error(14);
zlibUncompress(compressedText, compressedTextSize, arr);
}
else
{
// then it isn't zlib compressed and we are sunk
#ifdef DEBUG
std::cerr << "Exiv2::PngChunk::parsePngChunk: Non-standard iTXt compression method.\n";
#endif
throw Error(14);
}
}
else
{
#ifdef DEBUG
std::cerr << "Exiv2::PngChunk::parsePngChunk: We found a field, not expected though\n";
#endif
throw Error(14);
}
return arr;
} // PngChunk::parsePngChunk
void PngChunk::decode(Image* pImage,
const byte* pData,
long size,
int* outWidth,
int* outHeight)
{
assert(pImage != 0);
assert(pData != 0);
assert(outWidth != 0);
assert(outHeight != 0);
long index = 8;
// extract width and height from IHDR chunk, which *must* be the first chunk in the PNG file
if (strncmp((const char *)PNG_CHUNK_TYPE(pData, index), "IHDR", 4) == 0)
{
*outWidth = getLong((const byte*)&PNG_CHUNK_DATA(pData, index, 0), bigEndian);
*outHeight = getLong((const byte*)&PNG_CHUNK_DATA(pData, index, 4), bigEndian);
}
// look for a tEXt chunk
index += chunkLength(pData, index) + PNG_CHUNK_HEADER_SIZE;
while(index < size-PNG_CHUNK_HEADER_SIZE)
{
while (index < size-PNG_CHUNK_HEADER_SIZE &&
strncmp((char*)PNG_CHUNK_TYPE(pData, index), "tEXt", 4) &&
strncmp((char*)PNG_CHUNK_TYPE(pData, index), "zTXt", 4) &&
strncmp((char*)PNG_CHUNK_TYPE(pData, index), "iTXt", 4))
{
if (!strncmp((char*)PNG_CHUNK_TYPE(pData, index), "IEND", 4))
throw Error(14);
index += chunkLength(pData, index) + PNG_CHUNK_HEADER_SIZE;
}
if (index < size-PNG_CHUNK_HEADER_SIZE)
{
// we found a tEXt, zTXt, or iTXt field
// get the key, it's a null terminated string at the chunk start
const byte *key = &PNG_CHUNK_DATA(pData, index, 0);
int keysize=0;
for ( ; key[keysize] != 0 ; keysize++)
{
// look if we reached the end of the file (it might be corrupted)
if (8+index+keysize >= size)
throw Error(14);
}
DataBuf arr = parsePngChunk(pData, size, index, keysize);
#ifdef DEBUG
std::cerr << "Exiv2::PngChunk::decode: Found PNG chunk: "
<< std::string((const char*)key) << " :: "
<< std::string((const char*)arr.pData_, 32) << "\n";
#endif
parseChunkContent(pImage, key, arr);
index += chunkLength(pData, index) + PNG_CHUNK_HEADER_SIZE;
}
}
} // PngChunk::decode
