Question

i’ve a pyramidal tiled tiff file and I want to extract the tiles without decoding and re-encoding the jpeg, i’ve seen that using TIFFReadRawTile() function you can extract the raw tile without decoding, how can i write the extracted buffer to a readable jpeg file?

Answer 1

I’ve found that actually there is no way to get the encoded tile without directly messing with the huffmann tables of the tiff, which is pretty tricky.

The only way I’ve found is to read the decoded tile and then do some magic with vips to output to jpeg directly.

tdata_t buf;
tsize_t len;

buf = _TIFFmalloc( TIFFTileSize( tif ) );
len = TIFFReadEncodedTile(tif, tile, buf, (tsize_t) -1);

VImage result ((void *) buf, 256, 256, 3, VImage::FMTUCHAR);

void *outBuffer;
unsigned long len;
vips_jpegsave_buffer(result, &outBuffer, &len, "Q", 90, NULL);

and the use cout to output the image after some headers.