Re: Which scanners REALLY provide 36 bit output? HP?

From: Nick Lamb (
Date: Thu Dec 07 2000 - 21:45:45 PST

  • Next message: Paul Floyd: "Re: Which scanners REALLY provide 36 bit output? HP?"

    On Fri, Dec 08, 2000 at 12:17:17AM -0500, Bob Washburne wrote:
    > Scan a small image with bit depth set to 12 and save it as a png file.
    > Then look at that file with gimp and examine its properties. I believe
    > gimp will tell you what the color depth is. That should pretty much
    > confirm what is happening.

    Nope. "Consumer-grade" Gimp is an 8 bit per channel app, through to
    the core. You can load a 16-bit PNG image, but the color accuracy
    will be silently truncated. No ordinary releases of Gimp will include
    higher color accuracy for some time yet, mostly because so few people
    need it.

    If you want to do image processing of very accurate, very high res.
    images you should probably check out VIPS instead of, or as well as

    Using file(1) should enable you to detect if a PNG image is 8-bit or
    16-bit per sample. Note that not all SANE frontends can output more
    than 8-bits per sample anyway, I think XSane can.

    Both PNG and SANE only transport 8 bit or 16 bit units, so if the
    scanner is capable of any amount greater than 8 bits per sample, the
    results are dynamically scaled to fill a 16-bit sample, this process
    is of course reversible (see sBIT documentation).


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