[sane-devel] Limits on scan width Epson v500 Linux Epkowa

Alesh Slovak alesh.slovak at avasys.jp
Mon Mar 22 23:46:06 UTC 2010

Dan Blacker wrote:
> Hope someone can help me with my problem,
> There seems to be a limit in the Linux plugin for the Espon Perfection 
> v500 that prevents it from scanning the full width of the transparency 
> unit at resolutions above 3200dpi.
> This limit is not present under Windows.
> How can I go about getting this fixed? Is the source available for this 
> plugin?

We found that at least some of the plugin based scanners were unstable when 
scanning more than 32kb per line, so an artificial limit was put in place.

Unfortunately, the plugin source code is not available. However, the limitation 
is enforced in open source code.

This is very much untested and there is no guarantee it will work, but you can 
try the following:
  - download the latest iscan sources
  - at the very bottom of backend/channel-usb.c replace
      return (self->interpreter ? 32 : 128) * 1024;
      return 128 * 1024;
  - compile and install iscan
  - after installing iscan, modify the fs-blacklist file which is normally 
installed under /usr/share/iscan by removing the line that references the 
GT-X770 (this is the Japanese model name corresponding to the V500). This step 
may not be necessary and could cause other problems so try it only if you are 
still unable to get your desired results.

Because the iscan and plugin binary packages do a lot of setup stuff for you, 
when you install manually you will have to do all the setup yourself.
You may want to just install your custom compiled version on top of the 
installed binary packages to take advantage of all the free setup they give you.

Let me know if you have any further questions.

Happy scanning,
Alesh Slovak                    Linux Team -- AVASYS Corporation
alesh.slovak at avasys.jp          http://avasys.jp

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