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<TITLE>sane-devel: Re: Scanner Color Shift Problem</TITLE>
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<META NAME="Author" CONTENT="Steve Underwood (steveu@coppice.org)">
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<META NAME="Subject" CONTENT="Re: Scanner Color Shift Problem">
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<H1>Re: Scanner Color Shift Problem</H1>
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<!-- received="Fri Mar 2 06:32:55 2001" -->
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<!-- sent="Fri, 02 Mar 2001 22:50:24 +0800" -->
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<!-- isosent="20010302145024" -->
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<!-- name="Steve Underwood" -->
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<!-- subject="Re: Scanner Color Shift Problem" -->
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<!-- id="3A9FB330.499CF6CB@coppice.org" -->
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<!-- inreplyto="20010302124054.C5041@aruba.remote.org" -->
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<STRONG>From:</STRONG> Steve Underwood (<A HREF="mailto:steveu@coppice.org?Subject=Re:%20Scanner%20Color%20Shift%20Problem&In-Reply-To=<3A9FB330.499CF6CB@coppice.org>"><EM>steveu@coppice.org</EM></A>)<BR>
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<STRONG>Date:</STRONG> Fri Mar 02 2001 - 06:50:24 PST
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<LI><STRONG>Next message:</STRONG> <A HREF="0032.html">Ian Stirling: "Preview-when scanning?"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0030.html">Frederik Ramm: "Re: Scanner Color Shift Problem"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0030.html">Frederik Ramm: "Re: Scanner Color Shift Problem"</A>
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Frederik Ramm wrote:
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<BR>
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<EM>>
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</EM><BR>
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<EM>> Hi,
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> > This looks like a common colour merging problem. In most scanners there
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</EM><BR>
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<EM>> > is a physical separation between the red green and blue sensors. Most
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</EM><BR>
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<EM>> > scanners just feed data to the host with this separation, and the driver
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</EM><BR>
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<EM>> > needs to shuffle the scan lines to accurately merge the colours. You
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</EM><BR>
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<EM>> > will find code to perform this function in several sane backends. A
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</EM><BR>
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<EM>> > typical offset between each sensor row is 1/75 inch, but varies between
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</EM><BR>
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<EM>> > models.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> I know about that, and I've done the color merging "by the book" in my
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</EM><BR>
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<EM>> driver. Just to be on the safe side, I have changed the driver's
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</EM><BR>
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<EM>> offset by +/-1, and each time the error became even bigger. Then I
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</EM><BR>
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<EM>> tried the Windows driver that came with the product and it produced
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</EM><BR>
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<EM>> the same "error", so I have to assume it is a hardware problem.
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</EM><BR>
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<P>But your scan appears to have an error greater than a pixel. A 1 pixel
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<BR>
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shift in the right direction should surely make the result better than
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<BR>
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your sample scan. You didn't actually say what the resolution of your
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<BR>
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sample is, but there is definitely something wrong. Even cheap scanners
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<BR>
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show no percievable colour fringing at their maximum resolution. Its a
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<BR>
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pretty easy thing to get right.
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<BR>
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<P>Regards,
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<BR>
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Steve
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<BR>
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<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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To unsubscribe: echo unsubscribe sane-devel | mail <A HREF="mailto:majordomo@mostang.com?Subject=Re:%20Scanner%20Color%20Shift%20Problem&In-Reply-To=<3A9FB330.499CF6CB@coppice.org>">majordomo@mostang.com</A>
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</PRE>
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<LI><STRONG>Next message:</STRONG> <A HREF="0032.html">Ian Stirling: "Preview-when scanning?"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0030.html">Frederik Ramm: "Re: Scanner Color Shift Problem"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0030.html">Frederik Ramm: "Re: Scanner Color Shift Problem"</A>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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: <EM>Fri Mar 02 2001 - 06:34:04 PST</EM>
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