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64 wiersze
2.7 KiB
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<!-- received="Fri Mar 5 14:07:52 1999 PST" -->
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<!-- sent="Sat, 6 Mar 1999 00:20:36 +1100 (EST)" -->
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<!-- name="Jiri Baum" -->
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<!-- email="jiri@baum.com.au" -->
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<!-- subject="Re: Automatic Brightness and Contrast correction?" -->
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<title>sane-devel: Re: Automatic Brightness and Contrast correction?</title>
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<h1>Re: Automatic Brightness and Contrast correction?</h1>
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<b>Jiri Baum</b> (<a href="mailto:jiri@baum.com.au"><i>jiri@baum.com.au</i></a>)<br>
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<i>Sat, 6 Mar 1999 00:20:36 +1100 (EST)</i>
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<li> <b>Next message:</b> <a href="0063.html">Oliver Rauch: "xsane-0.14 available"</a>
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<li> <b>Previous message:</b> <a href="0061.html">Milon Firikis: "Re: another pre-test"</a>
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Håkan Kvarnström:<br>
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<i>> Does any one know how to achieve automated brightness and</i><br>
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<i>> contrast correction for scans made using SANE?</i><br>
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<p>
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Well, ppmnorm / pgmnorm would probably do most of what you're after... They<br>
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map the ligthest pixels to white, darkest to black and interpolate (you can<br>
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also give it the values manually). Check also pnmgamma, ppmbrighten,<br>
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ppmflash and probably some others I've missed.<br>
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<p>
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<i>> I have been experimenting with "ppmhist" to create histograms of images</i><br>
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<i>> which I used to calculate correction values for brightness and contrast.</i><br>
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<i>> The problem is that it requires me to scan the same image twice.</i><br>
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<p>
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If you want to set the brightness/contrast directly at the scanner, you'll<br>
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naturally have to do two scans; the first one might be just a quick<br>
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pre-scan. Even automatic photocopiers do a quick half-scan to set<br>
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brightness.<br>
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<p>
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<p>
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HTH<br>
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<p>
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Jiri<br>
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<pre>
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--
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<<a href="mailto:jiri@baum.com.au">jiri@baum.com.au</a>>
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We'll know the future has arrived when every mailer transparently
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quotes lines that begin with "From ", but no-one remembers why.
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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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<li> <b>Previous message:</b> <a href="0061.html">Milon Firikis: "Re: another pre-test"</a>
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