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From Tilman Hausherr <THaush...@t-online.de>
Subject Re: QR Image Detection Down 2.0.13 -> 2.0.14
Date Mon, 29 Apr 2019 11:47:06 GMT
Coincidentally:

  https://issues.apache.org/jira/browse/PDFBOX-4530

Tilman


Am 29.04.2019 um 11:15 schrieb STAMPF Lukas:
> Hello,
>
> Sorry for not responding earlier. I looked into it again with the release of 2.0.15 and
the difference is that bitonal rendering was also done with bicubic interpolation prior to
the rendering hints  implementation of 2.0.14. Setting the rendering hints to bicubic manually
on 2.0.15 restores the behavior of 2.0.13. Unfortunately I couldn't come up with a PDF I could
send you. Most of the documents I have that trigger this behavior are from production and
it seems that the problem occurs so rarely and depends on scanner quality that I couldn't
produce a PDF that reproduces this behavior.
>
> But I can guarantee that
> RenderingHints.VALUE_INTERPOLATION_NEAREST_NEIGHBOR / RenderingHints.VALUE_INTERPOLATION_BICUBIC
> Do not produce the same result on BINARY rendering and the change is the reason why my
QR detection rate went down.
>
> Kind regards,
> Lukas
>
>
>
> -----Ursprüngliche Nachricht-----
> Von: STAMPF Lukas <lukas.stampf@bat.at>
> Gesendet: Freitag, 5. April 2019 19:04
> An: users@pdfbox.apache.org
> Betreff: AW: QR Image Detection Down 2.0.13 -> 2.0.14
>
> Hi,
>
> I try to come up with an PDF I can send you.  But from a quick debug it seems that even
bitonal rendering happened with bicubic interpolation in 2.0.13.
>
> Have a nice weekend,
> Lukas
>
>
> -----Ursprüngliche Nachricht-----
> Von: Tilman Hausherr <THausherr@t-online.de>
> Gesendet: Freitag, 5. April 2019 18:42
> An: users@pdfbox.apache.org
> Betreff: Re: QR Image Detection Down 2.0.13 -> 2.0.14
>
> Am 05.04.2019 um 18:14 schrieb STAMPF Lukas:
>> Hi,
>>
>> I guess the reason for that is that if you set a single RenderingHint, you need to
provide all of them or lose the rest from Default.
> Yes.
>
>> By setting KEY_ANTIALIASING I essentially removed VALUE_RENDER_QUALITY and so it
didn't work.
>> But now the interesting part: By setting VALUE_RENDER_QUALITY I kept that setting,
but removed the KEY_INTERPOLATION setting.
> That would be that there would be no interpolation (VALUE_INTERPOLATION_NEAREST_NEIGHBOR),
which makes sense for bitonal destination.
>
>> I just checked: Setting KEY_RENDERING and KEY_ANTIALIASING and therefore removing
KEY_INTERPOLATION from the RenderingHints improved my situation on 2.0.14. Has something changed
there?
> No, unless I made a mistake... I took care that people get the same as before.
>
> I could research this, but then I'd need to get a PDF (please upload to a sharehoster).
>
> Tilman
>
>
>
>> Lukas
>>
>> -----Ursprüngliche Nachricht-----
>> Von: Tilman Hausherr <THausherr@t-online.de>
>> Gesendet: Freitag, 5. April 2019 17:55
>> An: users@pdfbox.apache.org
>> Betreff: Re: QR Image Detection Down 2.0.13 -> 2.0.14
>>
>> Hi,
>>
>> This is weird, RenderingHints.VALUE_RENDER_QUALITY is in the default settings?! See
in the source code, PDFRenderer.createDefaultRenderingHints().
>>
>> antialiasing is off when bitonal destination.
>>
>> Tilman
>>
>>
>> Am 05.04.2019 um 17:48 schrieb STAMPF Lukas:
>>> Thanks, seems like it wasn't the antialiasing. Turning it off and on didn't change
the results between 2.0.13 and 2.0.14. What did help however was
>>>                    hints.put(RenderingHints.KEY_RENDERING,
>>> RenderingHints.VALUE_RENDER_QUALITY);
>>>
>>> Setting this on 2.0.14 seems to restore the 2.0.13 behavior. Could be coincidence
though. Need to verify it with a larger amount of documents first. Has something about this
setting changed between versions when rendering in BINARY mode?
>>>
>>> Lukas
>>>
>>> -----Ursprüngliche Nachricht-----
>>> Von: Tilman Hausherr <THausherr@t-online.de>
>>> Gesendet: Freitag, 5. April 2019 17:00
>>> An: users@pdfbox.apache.org
>>> Betreff: Re: QR Image Detection Down 2.0.13 -> 2.0.14
>>>
>>> Yes, PDFRenderer now allows to pass rendering hints.
>>>
>>> Tilman
>>>
>>> Am 05.04.2019 um 16:42 schrieb STAMPF Lukas:
>>>> Hi,
>>>>
>>>> I am using  PDFBox to generate BufferedImages  which I feed to ZXing
>>>> 3.3.3 to do QR scanning. When I updated from 2.0.13 to 2.0.14 I
>>>> noticed a severe reduction in scanning reliability. I guess its
>>>> related to this change
>>>> https://issues.apache.org/jira/browse/PDFBOX-4391
>>>>
>>>> This is the render command I use:
>>>>                 bim = pdfRenderer.renderImageWithDPI(pageCounter,
>>>> dpi, ImageType.BINARY);
>>>>
>>>> I try multiple dpi settings between 150 and 300, to increase my changes to
find a QR code.
>>>> Is there some flag I can set to test out if the antialiasing causes this?
>>>>
>>>> Kind regards
>>>>
>>>>
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