2005.03.22 20:00 "Re: [Tiff] tif_jpeg.c and 12bit JPEG Files", by David Gilbert
The only way that makes sense is for 12 bit samples to be returned the same as for an uncompressed 12 bit TIFF file. Likewise, 12 bit samples should be consumed so that the only thing special the library user needs to do is request JPEG compression, and possibly JPEG RGB mode.
Well... the "issue" is that the jpeg library treats 12 bit samples as 12 bit stored in 16 bit integers. JPEG's transformation uses 16 bit ints for the math anyways... so someone has to do the upsampling. Both the classic and the MK1 jpeg expect the user to do this.
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