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

[Alesh Slovak]

> Hi Alesh,
> 
> Thanks for your help,
> 
> I uninstalled iscan, downloaded the latest installer and also the source.
> 
> I installed iscan from the .deb file
> 
> Then extracted the source into a folder, and made the modifications to 
> channel-usb.c.
> 
> I ran:
> 
>   sudo ./configure
>   sudo make
>   sudo make install
> 
> All ran with no errors.
> 
> Tried scanning the full width of the TPU at 4800dpi in iscan, got the 
> same old error:
> 
>   Selected area is too large for this resolution. Reduce the selected 
> area or resolution
> 
> Removed the line from the fs-blacklist file, and still the same error.
> 
> Is there a way to double check that my compiling of the source is being 
> used correctly?
> 
> Thanks,
> Dan

Hi Dan,

I've CC'ed the list for reference.

 From what you've told me, and digging around a bit, I think I've figured out 
the root of the problem you are having.

At high resolutions the V500's supported resolution list for the TPU in the X 
and Y directions are completely different. The highest common resolution in both 
directions is 1600 dpi. iscan, in the interest of usability, hides this 
complexity from you and attempts to compensate by doing some scaling behind your 
back. However, due to a bug in its image processing library it refuses to 
process such large images. Hence the error you are getting which happens to be 
the same as before, but with a different root cause.

You should be able to scan with scanimage or XSANE, but will have to keep in 
mind that unlike iscan, these frontends do not hide the resolution mess from 
you, and you will have to specify a different X and Y resolution when scanning 
at higher resolutions. The end result is that your images will come out 
stretched in one direction or the other. You will have to rescale your images 
manually using the Gimp or another tool. I would personally recommend using the 
Image Magick command line tools in a script to automate the scanning and scaling 
process, if that is possible with your workflow.

If you can scan a colour image with a width greater than 11,000 pixels using 
scanimage, then you are definitely using the modified code. With iscan it is 
uncertain due to all the things it tries to do behind your back.

Looking at the information I have, the maximum width you could possibly get out 
of the V500's TPU is 17,280 pixels @ 6400 dpi. This definitely requires the code 
modification and editing of the fs-blacklist as I instructed you before.


I hope all this made some sense.
Let me know if you can get it to work.

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