[sane-devel] option threshold without effect for fujitsu backend since 1.0.24-1

[m. allan noah]

It looks like commit 96628ed13f411298ee0681e7515745fdf85d1309 is the
culprit. This change enabled the image processing functions by
default, but that seems to have disabled the threshold algorithm in
the scanner. I will look for an alternative implementation.

allan

On Tue, Oct 4, 2016 at 7:49 PM, m. allan noah <kitno455 at gmail.com> wrote:
> Mickael, thank you for the report. I thought I had fixed this problem
> previously, but I am apparently wrong. I will investigate.
>
> allan
>
> On Mon, Oct 3, 2016 at 12:13 PM, PELUARD Mickael
> <mickael.peluard at smart-rx.com> wrote:
>> Hello,
>>
>>
>>
>>                 we used Fujitsu scanner (fi-5110 / fi-5120 / fi-6110) for a
>> long time with an old linux plateform and sane (1.0.22-9). These scanners
>> used the fujitsu backend.
>>
>>
>>
>>                 We have recently changed to RHEL-6 with sane-backends-1.0.21
>> and to Debian with libsane-1.0.25.
>>
>>
>>
>>                 We scan in lineart mode and we only put the threshold option
>> to reduce the size of document : scanimage –d ‘fujitsu:XXX:XXX’ --resolution
>> 150  --mode lineart  --threshold 140
>>
>>                 Then we convert the image to PDF-A1. With the old plateform
>> and rhel-6, no problem. But with Debian and sane-1.0.25, the size of the
>> documents increase a lot.
>>
>>
>>
>> Using a reference document, we get the following results with a fi-6110 :
>>
>> -          Rhel-6 / sane-1.0.21 = around 50 ko
>>
>> -          Debian / sane-1.0.25-2 = around 350 ko
>>
>> It’s quite the same problem if we used a fi-5110c and fi-5120c.
>>
>>
>>
>> I downgrade the libsane package and look the result :
>>
>> -          Debian / libsane-1.0.22-7 = good
>>
>> -          Debian / libsane-1.0.23-3+b1 = good
>>
>> -          Debian / libsane-1.0.24-1 = NOT GOOD
>>
>> -          Debian / libsane-1.0.24-8u5 = NOT GOOD
>>
>> -          Debian / libsane-1.0.26Git = NOT GOOD
>>
>>
>>
>> I change the value of threshold on Debian with sane-1.0.25 : threshold 0 or
>> 200. But the image don’t change. It’s look like the threshold option has not
>> effect.
>>
>> To reduce the problem, I play with the contrast and brightness option but
>> the result is not entirely satisfactory.
>>
>>
>>
>> I think the problem is on the threshold option of the fujitsu backends.
>>
>>
>>
>> It is probably the same bug but it don’t lokk corrected in 1.0.26 :
>>
>> https://alioth.debian.org/tracker/?group_id=30186&atid=410366&func=detail&aid=315069
>>
>>
>>
>> Cordially.
>>
>>
>> --
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>
>
>
> --
> "well, I stand up next to a mountain- and I chop it down with the edge
> of my hand"



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