sane-project-website/old-archive/1999-06/0226.html

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<title>sane-devel: Re: calculation of bytes to read, bytes per line etc</title>
<h1>Re: calculation of bytes to read, bytes per line etc</h1>
<b>abel deuring</b> (<a href="mailto:a.deuring@satzbau-gmbh.de"><i>a.deuring@satzbau-gmbh.de</i></a>)<br>
<i>Mon, 28 Jun 1999 18:42:05 +0200</i>
<p>
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Hi Meino !<br>
<p>
<i>&gt;  Unfortunatly, there most be some round errors or</i><br>
<i>&gt;  something like that, cause Xscanimage gets (or means)</i><br>
<i>&gt;  a greater amount of bytes to read, than my scanner is</i><br>
<i>&gt;  willing to send.</i><br>
<p>
If it is possible for the Avision scanner, an easy and reliable solution<br>
would be to ask the scanner how many bytes it will return for a scan:<br>
The frontends call sane_get_parameters after a scan is started in order<br>
to get the real scan size. <br>
<p>
Several backends have the function sane_get_parameters implemented like<br>
this:<br>
<p>
SANE_Status sane_get_parameters(SANE_Handle handle, SANE_Parameters<br>
*params)<br>
{<br>
  Scanner *s = handle;<br>
<p>
  if (!s-&gt;scanning) {<br>
    /* estimate the number of pixel per line and the number of<br>
       scan lines based on the selected resolution, scan window<br>
       size etc., and set *params accordingly<br>
    */<br>
    ...<br>
  }<br>
  else {<br>
    /* the scanner has received a "set window" and a "start scan"<br>
       command; now ask the scanner how many pixels per line<br>
       and how many lines it will send. Set *params accordingly<br>
    */<br>
    ...<br>
  }<br>
}<br>
<p>
Abel<br>
<p>
<pre>
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<li> <b>Next message:</b> <a href="0227.html">joel@cs.rochester.edu: "Re: X6EL modes under OS/2?"</a>
<li> <b>Previous message:</b> <a href="0225.html">Oliver Rauch: "XSANE-0.27 available"</a>
<li> <b>Maybe in reply to:</b> <a href="0220.html">Meino Christian Cramer: "calculation of bytes to read, bytes per line etc"</a>
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