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<!-- received="Fri Feb 20 15:05:35 1998 PST" -->
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<!-- sent="Fri, 20 Feb 1998 17:28:06 +0100 (MET)" -->
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<!-- name="Rogier Wolff" -->
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<!-- email="R.E.Wolff@BitWizard.nl" -->
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<!-- subject="Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way" -->
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<!-- id="199802201628.RAA01177@cave.BitWizard.nl" -->
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<!-- inreplyto="199802200845.JAA01668@cave.BitWizard.nl" -->
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<title>sane-devel: Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way</title>
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<h1>Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way</h1>
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<b>Rogier Wolff</b> (<a href="mailto:R.E.Wolff@BitWizard.nl"><i>R.E.Wolff@BitWizard.nl</i></a>)<br>
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<i>Fri, 20 Feb 1998 17:28:06 +0100 (MET)</i>
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<p>
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<ul>
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<li> <b>Messages sorted by:</b> <a href="date.html#118">[ date ]</a><a href="index.html#118">[ thread ]</a><a href="subject.html#118">[ subject ]</a><a href="author.html#118">[ author ]</a>
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<li> <b>Next message:</b> <a href="0119.html">Oliver.Rauch@Wolfsburg.DE: "Astra 6X0S-patch"</a>
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<li> <b>Previous message:</b> <a href="0117.html">David Skoll: "Linux 2.0.33 and Sane 0.70"</a>
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<li> <b>In reply to:</b> <a href="0115.html">Rogier Wolff: "Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way"</a>
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</ul>
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Rogier Wolff wrote:<br>
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<i>> </i><br>
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<i>> <a href="mailto:becka@rz.uni-duesseldorf.de">becka@rz.uni-duesseldorf.de</a> wrote:</i><br>
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<i>> > </i><br>
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<i>> > > </i><br>
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<i>> > > For example, with a float ccd of .12, I take 88% (100-12) of the current</i><br>
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<i>> > > line + 12% of the above line for blue channel and 76% (100-12*2) of the</i><br>
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<i>> > > current line + 24% (12*2) of the above line for the green channel. If</i><br>
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<i>> > > float ccd is <0, I swap the % values. [This is for Astra 610S, for 600S,</i><br>
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<i>> > > replace green with red].</i><br>
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<i>> > > </i><br>
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<i>> > > >From my point of view, this may lead to reduce image quality, but I</i><br>
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<i>> > > can't find another way to do this.</i><br>
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<i>> > </i><br>
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<p>
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I see that I've not been constructive, so let me post something<br>
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contstructive today :-)<br>
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<p>
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You can easily "loose the floating point". This will make things somewhat<br>
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faster on most processors. <br>
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<p>
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This is elementary "fixed point calculations". <br>
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<p>
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<p>
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float ip;<br>
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int iip, ap;<br>
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int array [MAX_ARRAY];<br>
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<p>
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ip /* Interpolation position */ = ..... ;<br>
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<p>
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/* the "ip" can be a float value, if it is 33.4 we want 60% of the<br>
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33rd and 40% of the 34th value. */<br>
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<p>
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<p>
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ap = ip;<br>
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iip = (ip * 256) - (ap * 256);<br>
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<br>
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/* rv becomes 256 times the value you really want.... */ <br>
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rv = array[ap] * (256-iip) + array[ap+1] * (iip);<br>
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<p>
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/* so we scale it back. We could forget this if the output format <br>
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can use the extra bits... */<br>
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rv >>= 8; <br>
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<p>
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Regards, <br>
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<p>
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Roger. <br>
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<p>
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<pre>
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--
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If it's there and you can see it, it's REAL <a href="mailto:|___R.E.Wolff@BitWizard.nl">|___R.E.Wolff@BitWizard.nl</a> |
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<p>
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<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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<!-- body="end" -->
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<p>
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<ul>
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<!-- next="start" -->
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<li> <b>Next message:</b> <a href="0119.html">Oliver.Rauch@Wolfsburg.DE: "Astra 6X0S-patch"</a>
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<li> <b>Previous message:</b> <a href="0117.html">David Skoll: "Linux 2.0.33 and Sane 0.70"</a>
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<li> <b>In reply to:</b> <a href="0115.html">Rogier Wolff: "Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way"</a>
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<!-- nextthread="start" -->
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<!-- reply="end" -->
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</ul>
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