HP4200 SANE backend

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Oops --- my bad.

You are correct. When I mentioned 8bpp, what I meant was 8
bits per pixel per color and likewise for the 10 and 12 bit
numbers. Thus the scanner hardware scans at 32 bits per
pixel (12 per pixel per color * 3 colors = 36) and then uses
the first two bits to compensate for gain and offset and the
next two to compensate for gamma.

Sorry.

Dan

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Are we thinking of the same scanner here? the hp site claims
36 bpp for the entire series, and the windows drivers
produce output that looks >=24 bpp atleast.

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I'm not sure >8 bpp is realistically possible. While the
HP4200 scanner hardware will scan up to 12 bpp, the extra
bits do not turn themselves into extra resolution.
Instead, they still need to have offset/gain/gamma
correction applied to them.

If you correct for the offset and gain in the scanner
hardware, the result is a 10 bpp scan.

If you correct for gamma as well, the result is an 8bpp
scan which is what the current software provides.

Do you really want a 10 or 12 bpp scan, with color which is
more distorted than the current scans?

Dan