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79 wiersze
3.9 KiB
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<!-- received="Mon Apr 5 14:00:07 1999 PDT" -->
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<!-- sent="Mon, 5 Apr 1999 22:00:47 +0100 (BST)" -->
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<!-- name="Nick Lamb" -->
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<!-- email="njl98r@ecs.soton.ac.uk" -->
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<!-- subject="Re: 16 bit per sample support" -->
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<title>sane-devel: Re: 16 bit per sample support</title>
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<h1>Re: 16 bit per sample support</h1>
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<b>Nick Lamb</b> (<a href="mailto:njl98r@ecs.soton.ac.uk"><i>njl98r@ecs.soton.ac.uk</i></a>)<br>
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<i>Mon, 5 Apr 1999 22:00:47 +0100 (BST)</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#85">[ date ]</a><a href="index.html#85">[ thread ]</a><a href="subject.html#85">[ subject ]</a><a href="author.html#85">[ author ]</a>
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<li> <b>Next message:</b> <a href="0086.html">Jonathan A. Buzzard: "Re: 16 bit per sample support"</a>
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<li> <b>Previous message:</b> <a href="0084.html">Oliver Rauch: "xsane-0.20 available"</a>
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<li> <b>In reply to:</b> <a href="0077.html">Jonathan A. Buzzard: "Re: 16 bit per sample support"</a>
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</ul>
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I said:<br>
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<i>> There is no data loss (watch this...</i><br>
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<i>> 0xabc (12bit) --> 0xabca (16bit) --> 0xabc (12bit)</i><br>
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<i>> 0x123 (12bit) --> 0x1231 (16bit) --> 0x123 (12bit) </i><br>
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<p>
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Jonathan replies:<br>
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<i>> Because you have mugged the values. X-rays where only an example, but the</i><br>
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<i>> same could be said of other sources such as aerial photography etc.</i><br>
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<i>> With these sorts of things you often want to do calculations on the</i><br>
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<i>> scanned images.</i><br>
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<p>
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<i>> For example I might have three Xrays of an object, that after some sort</i><br>
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<i>> of registration I wish to stack on top of one another. The Xrays have</i><br>
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<i>> been scanned say at 12 bits, now if you have stretched them though to</i><br>
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<i>> the full dynamic range of 16 bits adding the pixel values together</i><br>
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<i>> will result in loss of information. If they had stayed as 12 bits inside</i><br>
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<i>> a 16 bit value there is no problem.</i><br>
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<p>
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If you really must have back the 12-bit data you can do the second transform<br>
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I showed, and get back the 12-bit data. There is no data loss involved. For<br>
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most applications it is appropriate to use the full dynamic range, but you<br>
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are right that some software will lose data working on 16-bit images. IMHO<br>
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this software is broken (but I would say that because the tools I'm using<br>
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don't have this problem)<br>
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<p>
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The feature you describe (an additional toggle setting for stretch vs<br>
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truncate) seems excessive even for Advanced options, where it will probably<br>
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confuse users in a less technical environment. I don't think we want the<br>
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advanced setting to mean "Deep magic for image processing people".<br>
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<p>
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If this level of accuracy (probably beyond human vision) is required for your<br>
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application, you should suspect a lot of other components (optical problems<br>
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at capture stage, development process, scanner hardware, ADC) before SANE.<br>
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<p>
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Nick.<br>
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<p>
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Check out <a href="http://godzilla.ecs.soton.ac.uk:8888/images.html">http://godzilla.ecs.soton.ac.uk:8888/images.html</a><br>
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for Accurate Color, High Resolution images delivered to a perfectly<br>
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ordinary web browser (with Javascript and Java)<br>
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<p>
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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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To unsubscribe: echo unsubscribe sane-devel | mail <a href="mailto:majordomo@mostang.com">majordomo@mostang.com</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="0086.html">Jonathan A. Buzzard: "Re: 16 bit per sample support"</a>
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<li> <b>Previous message:</b> <a href="0084.html">Oliver Rauch: "xsane-0.20 available"</a>
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<li> <b>In reply to:</b> <a href="0077.html">Jonathan A. Buzzard: "Re: 16 bit per sample support"</a>
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</ul>
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