Re: [gscan2pdf-help] Resolution options with Epson Workforce 645 all in one

[Jeff <jf...@po...>]

On 09/03/17 04:33, Jim Mayer wrote:
> Strangely, I'm pretty sure it's the same driver. The "epkowa" SANE
> driver is the one provided by Epson for use with iscan. I think they
> either ignore the returned data or are scaling the image. To check
> this out, I switched the gscan2pdf front end to "scanimage" and
> hand-edited the cached resolution information in $HOME/.gscan2pdf to
> include a "150" dpi option. Selecting that option produced a 150dpi
> output with the expected size and number of pixels. Unsurprisingly,
> though adding a bizarre "126dpi" option scanned and reported the
> requested resolution, the number of pixels matched the 150dpi setting.

Some backends provide conf files. On my Debian testing system, these are
in /etc/sane.d/. If you are lucky, you might be able to affect the
options presented by editing the appropriate file.

There are other files in /usr/share/sane. On my system, they don't seem
to be useful.

You might be able to hack the source of the epkowa backend. I had a
quick scan through it, but couldn't find where the options are defined.

> Also, I thought of another workaround, but you might not like it.
> Since the driver reports "150" as valid for the "x-resolution" and
> "y-resolution", it would work, at least in this case, to add any value
> that showed up in both the "x-resolution" and "y-resolution" lists to
> the "resolution" list. The behavior could be controlled by a switch or
> an environment variable. I admit that it's kind of gross, and I did
> notice that the code is pretty rigorous about not playing with the
> values that SANE reports.

You're right. I don't like it, as it introduces whole new ways of
breaking things, and some SANE backends don't seem very good at dealing
with errors.

However, in order to do thing properly, I would like to confirm the
logic. Please give me the geometry of the images produced by the following:

scanimage --x-resolution 150 --y-resolution 150 --resolution 75

scanimage --y-resolution 300 --resolution 75 --x-resolution 150

scanimage --resolution 75 --x-resolution 150 --y-resolution 300

Regards

Jeff