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

[Dan Blacker]

Hi Alesh,

My prefered workflow is to use Vuescan, as opposed to xsane, or scanimage.

When scanning the full width of the TPU with vuescan at 6400dpi, there are
no error messages, but vuescan automatically scans the image at 3200dpi
instead.

Do you know if I can set these X and Y resolutions differently in iscan?

I will do some more testing later - but If I can't get this working I was
considering upgrading to an Epson v700. Does this have similar problems? Or
as I understand it, is it handled by a different driver.

Thanks for all your help,
Dan




On 24 March 2010 01:15, Alesh Slovak <alesh.slovak at avasys.jp> wrote:

> 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
>
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