[sane-devel] Degrading images: Plustek OpticPro UT16

[Olaf Meeuwissen]

Hi rhn,

rhn writes:

> On Fri, 23 Sep 2016 10:40:35 +0200 (CEST)
> Johannes Meixner <jsmeix at suse.de> wrote:
>
>> Hello,
>> 
>> On Sep 22 18:33 rhn wrote (excerpt):
>> > the scanner I am using has a peculiar problem, where scanning
>> > consecutive images causes the image quality to degrade:
>> > the left part becomes yellow in vertical streaks that increase
>> > in numbers; the right part becomes red. To get a completely
>> > yellow-red image, about 10 scans are necessary, regardless
>> > of options.
>> > The backend for this scanner is plustek.  
>> 
>> at openSUSE we have an issue report with similar symptoms
>> but different backend (HP Scanjet 2400, genesys backend):
>> 
>> https://bugzilla.opensuse.org/show_bug.cgi?id=905034
>> 
>> I was unable to reproduce it or debug the root cause
>> so that all I did was basically blind guess, e.g. see:
>> 
>> https://bugzilla.opensuse.org/show_bug.cgi?id=905034#c18

> Thanks for pointing out that bug report.

Read the bug report.  Scan artifacts getting progressively worse during
a scan.

> I think that my issue might be different. I forgot to mention, but
> starting a new scan (second scanimage command) yields the same
> results, i.e. first 2 pages are fine.

So starting a new scan process will give you a good initial image or two
but then things go downhill.

Just a thought but could this be caused by forgetting to (re)initialize
reused dynamically allocated memory at the right times?  Like at the
start of every *image* (in sane_start()) rather than with every call of
sane_open() (or even worse, sane_init()).

In your case, the backend implementation may not have expected to be
used for consecutive image acquisition to begin with (bad!).  But it can
also be due to changes in the implementation defined behaviour of memory
functions or dependent on what the kernel does with released resources.

> I managed to get the git build to run locally, and I'm testing it, so
> my initial question is answered.
>
> I suspect my hardware is shot and needs extra resets. Is there any
> other user of UT16 that can confirm?

Hope this helps,
-- 
Olaf Meeuwissen, LPIC-2            FSF Associate Member since 2004-01-27
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