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April 2005
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2005.05.02 18:17 "Re: Color TIFF/JPEG compression questions", by Jason Frank
Thanks for the schooling. That shiny new JPEG compression scheme is
really quite clever. I've taken a look at the code for tif_print.c, and
it looks correct. It goes like this:
if (TIFFFieldSet(tif,FIELD_YCBCRSUBSAMPLING))
{
/*
* For hacky reasons (see tif_jpeg.c -
JPEGFixupTestSubsampling),
* we need to fetch this rather than trust what is in our
* structures.
*/
uint16 subsampling[2];
TIFFGetField( tif, TIFFTAG_YCBCRSUBSAMPLING,
subsampling + 0, subsampling + 1 );
fprintf(fd, " YCbCr Subsampling: %u, %u\n",
subsampling[0], subsampling[1] );
}
I didn't find any redefinitions of TIFFTAG_YCBCRSUBSAMPLING, and I
didn't see any suspicious TiffSetFields in tiffinfo.c either. I did
notice that tiffdump said:
YCbCrSubsampling (530) SHORT (3) 2<2 2>
On the very last line.
So, I think that tiffinfo might be playing correctly here (since it
agrees with tiffdump, and I don't see any obvious problems with the
code.)
Jason