kopia lustrzana https://gitlab.com/sane-project/website
68 wiersze
3.2 KiB
HTML
68 wiersze
3.2 KiB
HTML
<!-- received="Sat Apr 24 09:02:33 1999 PDT" -->
|
||
<!-- sent="Sat, 24 Apr 1999 17:03:54 +0100 (BST)" -->
|
||
<!-- name="Nick Lamb" -->
|
||
<!-- email="njl98r@ecs.soton.ac.uk" -->
|
||
<!-- subject="Re: lineart vrs greyscale" -->
|
||
<!-- id="" -->
|
||
<!-- inreplyto="3721D91D.7931F316@kootenay.com" -->
|
||
<title>sane-devel: Re: lineart vrs greyscale</title>
|
||
<h1>Re: lineart vrs greyscale</h1>
|
||
<b>Nick Lamb</b> (<a href="mailto:njl98r@ecs.soton.ac.uk"><i>njl98r@ecs.soton.ac.uk</i></a>)<br>
|
||
<i>Sat, 24 Apr 1999 17:03:54 +0100 (BST)</i>
|
||
<p>
|
||
<ul>
|
||
<li> <b>Messages sorted by:</b> <a href="date.html#344">[ date ]</a><a href="index.html#344">[ thread ]</a><a href="subject.html#344">[ subject ]</a><a href="author.html#344">[ author ]</a>
|
||
<!-- next="start" -->
|
||
<li> <b>Next message:</b> <a href="0345.html">Faisal Nasim: "Re: Where is ScanImage in the RPM?"</a>
|
||
<li> <b>Previous message:</b> <a href="0343.html">Bob van der Poel: "lineart vrs greyscale"</a>
|
||
<!-- nextthread="start" -->
|
||
<!-- reply="end" -->
|
||
</ul>
|
||
<!-- body="start" -->
|
||
<i>> I was scanning some documents last night using my Microtek E3. I figured</i><br>
|
||
<i>> that since the text was straight black and white that I should use the</i><br>
|
||
<i>> lineart setting. Even at 300dpi the result was unreadable. Using</i><br>
|
||
<i>> greyscale produced nice docs.</i><br>
|
||
<p>
|
||
<i>> So, what's going on? When I select lineart or whatever, I assume that</i><br>
|
||
<i>> this is setting the scanner to scan in a particular mode...so shouldn't</i><br>
|
||
<i>> it be able to resolve b/w text better in lineart mode?</i><br>
|
||
<p>
|
||
The scanner hardware actually resolves greyscale, and lineart mode sets<br>
|
||
a threshold, just like the filter of the same name in e.g. GIMP. So<br>
|
||
the results of the threshold would pick up black-on-white art work while<br>
|
||
ignoring the noise from the grain of the paper, smudges etc. For text<br>
|
||
this is probably not what you want, unless you have an algorithm which<br>
|
||
works only on BW data, perhaps some OCR does this?<br>
|
||
<p>
|
||
To the human eye greyscale will always look better because it reduces<br>
|
||
aliasing. So if you're just going to look at the results (or use an<br>
|
||
algorithm which permits greyscale) you should use greyscale.<br>
|
||
<p>
|
||
The other advantage of line art is that it returns much less data (of<br>
|
||
course 8 times less normally, or better with RLE) and so can be saved<br>
|
||
to a smaller file and transmitted more quickly over SCSI. This might be<br>
|
||
important for scanning A4 documents at high resolution quickly.<br>
|
||
<p>
|
||
NB. You should be able to get *acceptable* results if you can tune the<br>
|
||
brightness or threshold parameters for the scanner hardware. I can get<br>
|
||
readable text from 400dpi lineart with the ScanJet IIc here.<br>
|
||
<p>
|
||
Nick.<br>
|
||
<p>
|
||
<p>
|
||
<pre>
|
||
--
|
||
Source code, list archive, and docs: <a href="http://www.mostang.com/sane/">http://www.mostang.com/sane/</a>
|
||
To unsubscribe: echo unsubscribe sane-devel | mail <a href="mailto:majordomo@mostang.com">majordomo@mostang.com</a>
|
||
</pre>
|
||
<!-- body="end" -->
|
||
<p>
|
||
<ul>
|
||
<!-- next="start" -->
|
||
<li> <b>Next message:</b> <a href="0345.html">Faisal Nasim: "Re: Where is ScanImage in the RPM?"</a>
|
||
<li> <b>Previous message:</b> <a href="0343.html">Bob van der Poel: "lineart vrs greyscale"</a>
|
||
<!-- nextthread="start" -->
|
||
<!-- reply="end" -->
|
||
</ul>
|