[sane-devel] epsonds backend ADF size with ES-50

[m. allan noah]

With some brands of scanners, there can be limitations in things like
resolution or bit depth when you enable larger size scans. So, be careful
assuming you want to always use that mode.

allan

On Wed, Aug 31, 2022 at 12:58 PM Ralph Little <skelband at gmail.com> wrote:

> Hi,
>
> On Tue, Aug 30, 2022 at 10:36 PM Sean Greenslade <sean at seangreenslade.com>
> wrote:
>
>> Hi, all. I recently picked up an Epson ES-50 sheet-feed scanner. My
>> intent is to use it for receipt scanning, so I tried it out with a
>> ~700 mm long receipt and found that it would error out at around 450 mm
>> into the scan. The manual claims the scanner is capable of a max of 72
>> inch document length, so I started poking around in the epsonds backend
>> code.  Something that jumped out at me was the eds_set_adf_area
>> function. It seems that for this particular scanner, three ADF size
>> values are reported: AREA, AMIN, and AMAX (in epsonds-cmd.c around line
>> 445 on current git master). The eds_set_adf_area function is called with
>> the values from AREA, which limits the document length to 14 inches. I'm
>> assuming AREA is just meant to be a default value, but if anyone has any
>> deeper insight into the meaning, I'd be interested to know.
>>
>
> Looking at that code, AMIN and AMAX are pretty much ignored.
> What do you get for all of the AREA/AMIN/AMAX parameters?
> Perhaps we can figure out what they mean and code up something a little
> better?
>
>
>>
>> The AMAX values reported seemed to match the manual's reported 72-inch
>> maximum, so on a whim, I just moved the eds_set_adf_area call to the
>> AMAX section. After recompiling, I was able to scan my long receipt no
>> problem.
>>
>> Now I'm wondering if there is any downside to using the max ADF size? If
>> not, would you consider the attached patch?
>>
>>
> I don't believe that we have a current maintainer for this backend
> although we do get some submissions from Epson Japan now and then for new
> models. I wonder if they would be willing to shed some light on this or
> provide us some documentation on this aspect of the protocol?
>
> Cheers,
> Ralph
>


-- 
"well, I stand up next to a mountain- and I chop it down with the edge of
my hand"
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