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<TITLE>sane-devel: Re: SnapScan</TITLE>
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<META NAME="Author" CONTENT="Steve Underwood (steveu@coppice.org)">
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<META NAME="Subject" CONTENT="Re: SnapScan">
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<H1>Re: SnapScan</H1>
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<!-- received="Fri May 5 08:13:00 2000" -->
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<!-- sent="Fri, 05 May 2000 23:13:14 +0800" -->
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<!-- name="Steve Underwood" -->
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<!-- email="steveu@coppice.org" -->
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<!-- subject="Re: SnapScan" -->
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<!-- id="3912E50A.5868AA98@coppice.org" -->
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<!-- inreplyto="00050418391400.00383@oliverspc" -->
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<STRONG>From:</STRONG> Steve Underwood (<A HREF="mailto:steveu@coppice.org?Subject=Re:%20SnapScan&In-Reply-To=<3912E50A.5868AA98@coppice.org>"><EM>steveu@coppice.org</EM></A>)<BR>
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<STRONG>Date:</STRONG> Fri May 05 2000 - 08:13:14 PDT
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<LI><STRONG>Next message:</STRONG> <A HREF="0043.html">Karlheinz G<>nster: "Re: Transparency support for snapscan backend"</A>
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<UL>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0041.html">Oliver Schwartz: "Re: SnapScan"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0036.html">Oliver Schwartz: "Re: SnapScan"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0007.html">Petter Reinholdtsen: "Re: SnapScan"</A>
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<HR NOSHADE><P>
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<P>
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Oliver Schwartz wrote:
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<BR>
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<P><EM>> > > I have an Acer ScanPrisa 620 UT. It works, but the RGB offsets are noticeable.
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</EM><BR>
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<EM>> >
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</EM><BR>
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<EM>> > Maybe the overhead (transparency unit) lamp *needs* special
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</EM><BR>
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<EM>> > calibration? The manual for the Prisa 620ST states that when
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</EM><BR>
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<EM>> > scanning slides or negs you must use the supplied mask and you
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</EM><BR>
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<EM>> > must leave the calibration window in this mask unobstructed.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> Yes, that's correct. And of course I'm using the mask in transparency mode. I
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</EM><BR>
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<EM>> have the impression that the calibration is done by the firmware - at least the
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</EM><BR>
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<EM>> trays move to the calibration area before each scan.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> The offsets appear in flatbed and transparency mode, though.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> However, the RGB offsets as I understand them are not an offset in value but a
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</EM><BR>
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<EM>> spatial offset. E. g. if you scan a black square on white background in
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</EM><BR>
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<EM>> color mode it doesn't have sharp edges but maybe a blue edge on one side and an
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</EM><BR>
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<EM>> orange edge on the other. Just try it.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> Oliver
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</EM><BR>
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<P>May the source be with you.......
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<BR>
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<P>If you look in the source for the snapscan module in Sane 1.0.2, and the code on the
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<BR>
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snapscan home page, you will see the code was undergoing heavy rework in the data
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<BR>
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buffering area at the time the author "abandoned" it. He seems to have finished
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everything but the colour offset handling. Dated comments state that this bit will be
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<BR>
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completed in the next few days, so that should give a pretty accurate indication of
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<BR>
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when he stopped work!
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<BR>
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<P>Older versions of the snapscan driver appear to have worked OK, using an older data
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<BR>
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buffering scheme with correct colour offset handling.
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<BR>
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<P>It seems to be possible to actually ask the scanner about the physical offsets
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<BR>
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between its three rows of CCD sesors, so handlign different models and revisions
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<BR>
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should be automatic. I'm currently working to implement proper offset handling using
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<BR>
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this. Watch this space....
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<BR>
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<P>Steve
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<BR>
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<P><P><P><PRE>
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--
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Source code, list archive, and docs: <A HREF="http://www.mostang.com/sane/">http://www.mostang.com/sane/</A>
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</PRE>
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<UL>
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<!-- next="start" -->
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<LI><STRONG>Next message:</STRONG> <A HREF="0043.html">Karlheinz G<>nster: "Re: Transparency support for snapscan backend"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0041.html">Oliver Schwartz: "Re: SnapScan"</A>
|
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<LI><STRONG>In reply to:</STRONG> <A HREF="0036.html">Oliver Schwartz: "Re: SnapScan"</A>
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<!-- nextthread="start" -->
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0007.html">Petter Reinholdtsen: "Re: SnapScan"</A>
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<EM>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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: <EM>Fri May 05 2000 - 08:20:45 PDT</EM>
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