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<H1>12bit (was Re: Patch for sane.tex (image polarity))</H1>
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<STRONG>From:</STRONG> Nick Lamb (<A HREF="mailto:njl98r@ecs.soton.ac.uk?Subject=Re:%2012bit%20(was%20Re:%20Patch%20for%20sane.tex%20(image%20polarity))&In-Reply-To=&lt;20001004204033.B1935@ecs.soton.ac.uk&gt;"><EM>njl98r@ecs.soton.ac.uk</EM></A>)<BR>
<STRONG>Date:</STRONG> Wed Oct 04 2000 - 12:40:33 PDT
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On Wed, Oct 04, 2000 at 12:10:38PM +0200, abel deuring wrote:
<BR>
<EM>&gt; (BTW, what happens, if [x]scanimage receives RGB data with, say, 12 bit
</EM><BR>
<EM>&gt; per colour? Is such a format handled properly by PNM programs or Gimp?)
</EM><BR>
<P>Can't happen. The SANE standard specifies 1bit, 8bit and 16bit only.
<BR>
<P>A backend which sends 12 bits per sample is broken. A backend which sends
<BR>
12 bits wrapped as 16 bits (with leading 000s) is broken. &quot;36 bit&quot; scanner
<BR>
data is multiplied (or at least shifted) to fill the dynamic range of
<BR>
16 bit samples before going over SANE. See (many) previous discussions
<BR>
in the list archives.
<BR>
<P>I don't know how PNM handles 16 bit, but Gimp provides only 8 bit samples
<BR>
and frontends like XSane and XScanimage are expected (required actually)
<BR>
to downsample if necessary before passing the data to Gimp.
<BR>
<P>Nick.
<BR>
<P><PRE>
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