[Digikam-users] digikam 4.2.0 : artefacts in previews

[Gilles Caulier]

Problem not reproducible here with your image.

There is an option in Setup/Album View to switch preview in full or
reduced size of image.

Libjpeg provide a way to reduce image size at loading time. Screen
resolution is used to estimate image size to load.

See my screenshot here :

https://www.flickr.com/photos/digikam/14835172186/

Here option is disabled. So reduced image size is loaded. Compared to
image editor on the right, image is smooth but do not have any
artefacts has you describe.

However, as i use WQHD flat screens, perhaps i'm not on the right
context to validate.

With 4.2.0 release we have introduced a new code to handle HQ screen
resolution has retina display from Apple. Entry in bugzilla is this
one :

https://bugs.kde.org/show_bug.cgi?id=337231

I check this code under Linux, OSX and Windows with different screen
sizes, and all work fine.

Perhaps screensize returned by your system is wrong.

I recommend to post a comment in this bugzilla file to have feedback
from original contributor and start investigations...

In all cases, the turn over on your system is to turn on option in
setup panel for the moment.

Note : you are not alone with this problem. See this comment :

https://www.digikam.org/node/715#comment-20800

Best

Gilles Caulier

2014-08-06 14:17 GMT+02:00 Robert Zeller <robert.zeller at robert-zeller.org>:
> Gilles,
>
> one more information on this issue:
> my jpgs are 36 Mpx big. To show the entire photo on my screen a zoom
> factor of 18% is used. If I zoom in to 50% or 100% the artifacts
> disappear. To me it looks like the problem is caused by the algorithm
> that reduces the picture view size to the screen size. I still have a
> copy of DK 4.1.0 which does not show this misbehavior. Something must
> have been changed between the two versions. Using Gimp I don't get any
> artifacts, however the Gnome Image viewer eog also produces the same
> kind of artifacts as DK 4.2.0.
>
> I came across one other issue in DK 4.2: When using : settings -->
> configure and switching between the different items in the configure
> menu, DK responses become extremely slow, and DK is using a lot of CPU
> power and it is not possible to cancel the configure window. What is the
> guy doing?
>
> Best regards,
>
> Robert
>
>
> On 08/06/2014 08:42 AM, Robert Zeller wrote:
>> Gilles,
>>
>> the files are too big to be sent by email. Please download the
>> screenshot and the original jpg from my web page:
>>
>> screenshot: www.robert-zeller.org/transfer/DK-4.2.0-artifact-shot.jpg
>> (see the strange pattern in the dome of the mosque and the poor resolution)
>>
>> original: www.robert-zeller.org/transfer/0012-SR-2014_05_06_170343.jpg
>> (file is about 15 MB)
>>
>> I don't see this behavior in previous versions of DK
>>
>> Best regards,
>>
>> Robert
>>
>>
>>
>> On 08/06/2014 12:06 AM, Gilles Caulier wrote:
>>> Can you take a shot and share a screenshot ?
>>>
>>> Problem is not visible here.
>>>
>>> Also, share some files to test here...
>>>
>>> Gilles Caulier
>>>
>>> 2014-08-06 0:00 GMT+02:00 Robert Zeller <robert.zeller at robert-zeller.org>:
>>>> Hello,
>>>>
>>>> I just compiled DK 4.2.0 on openSUSE 13.1 . There were no compilation
>>>> problems.
>>>> BUT: as compared to DK 4.1.0 I see on some photos a relatively strong
>>>> artifact (moirée) on regular structures. Also I have the impression that
>>>> the pictures are not loaded in full resolution. These artifacts seem to
>>>> disappear when using the image editor. Is there a way to remove the
>>>> moiree patterns? or to force DK to load pictures in full resolution?
>>>> Best regards,
>>>>
>>>> Robert
>>>>
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