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TIFF and LibTiff Mail List Archive

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2005.05.25 13:31 "[Tiff] Re[2]: Another libtiff+libjpeg problem", by Jean-Yves Le Ridant
2005.05.26 08:58 "Re: [Tiff] How to Write a tif file with c ompression = COMPRESSION_JPEG & photometr ic = PHOTOMETRIC_YCBCR ?", by yourpattern
2005.05.26 10:02 "Re[2]: [Tiff] How to Write a tif file wit h compression = COMPRESSION_JPEG & photom etric = PHOTOMETRIC_YCBCR ?", by yourpattern
[...]

2005.05.25 13:31 "[Tiff] Re[2]: Another libtiff+libjpeg problem", by Jean-Yves Le Ridant

KW> if your after a slightly better approximation but not too slow when KW> doing bit depth promotion you should fill the bottom bits with the

KW> upper bits...

KW> e.g. 12 bits to 16...

KW> 12 bits names
BA9876543210 ->> BA9876543210BA98

KW> The above being a bit shift

KW> out := (in << 4) | (in >> 8)

KW> 8 bits
76543210 ->> 7654321076543210

KW> it works and ensures that peak input is mapped to peak output.

:-))

Yes but...., unsigned shift is perfect for a and b of ICCLAB, and signed shift would be right for those of CIELAB ( and guys have strange ideas as jpeg compressing of CIELAB ...) :-)

No hope, really handling 16 bits is a job, and would be better handled by jpeglib interface, mixed with/in existing tables. So at this point it's obstensibely a quickwatch.

--
Jean-Yves