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<title>sane-devel: Re: JPEG scanner stuff</title>
<h1>Re: JPEG scanner stuff</h1>
<b>Stephen Williams</b> (<a href="mailto:steve@icarus.com"><i>steve@icarus.com</i></a>)<br>
<i>Wed, 04 Aug 1999 07:46:33 -0700</i>
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<a href="mailto:njl98r@ecs.soton.ac.uk">njl98r@ecs.soton.ac.uk</a> said:<br>
<i>&gt; What exactly comes out of your scanners? Is it just a JFIF standard</i><br>
<i>&gt; header followed by JPEG image data? </i><br>
<p>
Well, JFIF is really just an APP marker and some constraints on the<br>
JPEG stream that follows. DQT and DHT markers, and all the other required<br>
markers to make a fully formed JPEG compressed stream are present.<br>
So I'm not quite sure what you mean by "JFIF header followed by JPEG<br>
image data."<br>
<p>
If the image is color, I've had one component per scan, combined the<br>
color components in a scan, etc. The SOF marker describes the internal<br>
structure. The scanner boards have hardware jpeg compressors that can<br>
produce the JFIF images, with a little help from a micoprocessor.<br>
<p>
The IJG libjpeg software has no trouble reading these streams.<br>
<pre>
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Steve Williams "The woods are lovely, dark and deep.
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