Bug 256361 - SlideShow use low resolution previews instead of full resolution images
Summary: SlideShow use low resolution previews instead of full resolution images
Alias: None
Product: digikam
Classification: Applications
Component: Plugin-Generic-SlideShow (show other bugs)
Version: 4.8.0
Platform: Fedora RPMs Linux
: NOR normal
Target Milestone: ---
Assignee: Digikam Developers
Depends on:
Reported: 2010-11-08 12:50 UTC by Riccardo Gori
Modified: 2017-06-03 12:51 UTC (History)
5 users (show)

See Also:
Latest Commit:
Version Fixed In: 5.1.0

Screenshot of the problem (565.98 KB, image/png)
2010-11-08 15:00 UTC, Riccardo Gori

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Description Riccardo Gori 2010-11-08 12:50:04 UTC
Version:           1.5.0 (using KDE 4.5.2) 
OS:                Linux

I copied a folder (a new album) inside the root Pictures directory with the file manager and then opened DigiKam to view the photos. Trying to view a slideshow of the album results in the slideshow of low resolution previews.
I'm a long time DigiKam user and I experienced this problem with 1.5 version only.

Reproducible: Didn't try
Comment 1 caulier.gilles 2010-11-08 12:54:12 UTC
Do you talk about simple sideshow from digiKam core or Advanced Slideshow kipi-plugins ?

digiKam core slideshow has always used a reduced version with photo. With RAW we extract embeded JPEG preview. WithJPEG, we use a reduced preview computed by libjpeg.

It's work like this with preview mode from icon view (F3), and LightTable.

Gilles Caulier
Comment 2 Riccardo Gori 2010-11-08 13:11:49 UTC
It's the DigiKam simple slideshow, the kipi one works fine.

And the problem is just with one album imported with the new version of DigiKam. I rotated some images in the preview mode (and I can see them rotated in kipi-slideshow) but slideshow shows them with the old orientation (the previews are not updated).

All my old albums looks fine also with DigiKam slideshow, maybe because the preview resolution is bigger. I didn't find any settings to adjust the preview resolution to fit my screen's res.

Thanks for your fast response
Comment 3 caulier.gilles 2010-11-08 13:15:41 UTC
Sound like a problem with kipi jpeglossless tool.

Can you process a jpeg file and provide file before and after rotation ?

check of course if this processed file has a problem in slideshow...

Gilles Caulier
Comment 4 Riccardo Gori 2010-11-08 15:00:53 UTC
Created attachment 53245 [details]
Screenshot of the problem

Here is a screenshot of the problem (I disabled full size preview on preview mode).

The upper thumbnail of the photo have the correct orientation, the one shown by the preview is an old version (i.e. is not rotated).

The slideshow mode shows the same low-resolution and wrong rotation image.

The images are rotated correctly but the preview image is not updated.
Comment 5 Marcel Wiesweg 2010-11-08 18:23:17 UTC
So we can rename the bug "previews are not rotated when rotating full image"?
Comment 6 Riccardo Gori 2010-11-08 18:38:00 UTC
> So we can rename the bug "previews are not rotated when rotating full image"?

My main problem is still the very low resolution of the default slideshow for the new albums (or am I missing some new settings?).

I'll open a new bug for the previews updating issue.
Comment 7 Marcel Wiesweg 2010-11-08 21:59:35 UTC
The slideshow takes the desktop size as suggested preview size. With which type of photos do you have these problems? Please provide one for testing.
Comment 8 Riccardo Gori 2010-12-02 21:31:40 UTC
The preview size is wrong with 12Mpx photos (4000x3000).
Smaller photos, for instance 10Mpx (3872x2592) or 7Mpx (3072x2304), are displayed correctly.
I didn't try with bigger photos.
Comment 9 Mark van Rossum 2011-01-28 01:41:51 UTC
I have a similar problem w. digikam-1.7.0-1.fc14.1.kde46.i686.

That is, the slideshow images are lowres, you can see the jpeg artefacts.

I'm not sure when this bug started.
Comment 10 Reiner Nix 2011-11-21 20:38:57 UTC
I have a smiliar problem with digikam 2:1.9.0-3+b1 on debian testing since some versions. It appears only when locally logged into the computer but when running digikam using X display redirection to another computer (with slightly higher resolution) the slideshow uses full resolution. Also when using the extended slideshow the resolution is higher (but the used fonts for text have no high quality aliasing). My images are 14Mpx jpeg.

This bug occures for all images of my new albums. In addition to the discussed above, I do not need to rotate the images manually, as my camera has already set the orientation flag correctly.

Hope this info adds a bit more to get this nasty bug fixed.
Comment 11 caulier.gilles 2011-11-22 16:07:01 UTC
Which libjpeg you use ?

Can you provide an image sample to test in local (send it by mail or give an url)

Gilles Caulier
Comment 12 caulier.gilles 2011-12-15 17:36:08 UTC

I tested on my computer, using libjpeg 8.0 (Linux Mageia 1.0). No problem about image quality during slideshow with your image...

The proof : 


Note : I use dual screens...

Gilles Caulier
Comment 13 Reiner Nix 2011-12-18 22:28:49 UTC
Hello Gilles,

thanks for checking this. So we see that it does not depends on the image quality. Unfortunately this is still present on my pc. Do you have an idea why the problem occures when running digikam directly on the pc but it does not occure when forwarding the user interface to another host?
Comment 14 caulier.gilles 2011-12-19 07:06:00 UTC
What the difference between computer ? libjpeg ? screensize  ?

Gilles Caulier
Comment 15 Reiner Nix 2011-12-20 20:03:45 UTC
Let me try to describe the different scenarios:

Scenario 1: In the simple case, digikam is running on one host, named accius, which is - as usual - also the X-Server and directly connected to a monitor. Here the display resolution is 1280 x 1024 pixel.

Scenario 2: In the advanced case, digikam is still running on accius. But using the X-Window System, the user interface open its windows on another host, named vega. This is done using X Window display redirection. Thus vega is running the X-Server and displaying the windows. The host vega is connected to a flat screen TV, which is controlled by the regular graphics card of vega. Here a full HD resolution of 1920 × 1080 pixel is used.

So in both szenarios, the identical digikam installation on the same host is execured. In the first scenario the displayed image for a slideshow has poor quality but in the second scenario the slideshow provides the desired good quality.

I am using Debian Linux using the Testing branch with digikam 1.9.0 which is build against libjpeg62.
Comment 16 paul 2014-08-28 22:35:13 UTC
I don't know if people are still following this, but I wrote the following article recently which appears to describe this bug, or at least it resembles rather strongly the screenshot attached to comment #4.

Comment 17 caulier.gilles 2014-09-21 19:30:16 UTC
Git commit 05f67e3f6fe46b37221c7073c4e31b95532b3471 by Gilles Caulier.
Committed on 21/09/2014 at 19:26.
Pushed by cgilles into branch 'master'.

move slideshow info rendering code to dedicated widgets to simplify implementation in goal to use later a stack of widgets, support zoom feature, use main digiKam image preview cache, and play video files.
Related: bug 276480, bug 159824

M  +2    -0    CMakeLists.txt
A  +355  -0    utilities/slideshow/slideinfo.cpp     [License: GPL (v2+)]
A  +68   -0    utilities/slideshow/slideinfo.h     [License: GPL (v2+)]
A  +189  -0    utilities/slideshow/slideosd.cpp     [License: GPL (v2+)]
A  +72   -0    utilities/slideshow/slideosd.h     [License: GPL (v2+)]
M  +20   -378  utilities/slideshow/slideshow.cpp
M  +3    -4    utilities/slideshow/slideshow.h

Comment 18 caulier.gilles 2014-09-22 08:59:37 UTC
Git commit cafb796485f835f7ba172452c53edd247446eeb4 by Gilles Caulier.
Committed on 22/09/2014 at 08:58.
Pushed by cgilles into branch 'master'.

use QStackedWidget to show slide image view, slide error view, and slide end view
Related: bug 276480, bug 159824

M  +3    -0    CMakeLists.txt
A  +96   -0    utilities/slideshow/slideend.cpp     [License: GPL (v2+)]
A  +50   -0    utilities/slideshow/slideend.h     [License: GPL (v2+)]
A  +88   -0    utilities/slideshow/slideerror.cpp     [License: GPL (v2+)]
A  +61   -0    utilities/slideshow/slideerror.h     [License: GPL (v2+)]
M  +16   -0    utilities/slideshow/slideosd.cpp
M  +90   -188  utilities/slideshow/slideshow.cpp
M  +6    -6    utilities/slideshow/slideshow.h
A  +191  -0    utilities/slideshow/slideview.cpp     [License: GPL (v2+)]
A  +77   -0    utilities/slideshow/slideview.h     [License: GPL (v2+)]

Comment 19 caulier.gilles 2015-05-16 13:19:59 UTC
This file still valid using last digiKam 4.10.0 ?

Gilles Caulier
Comment 20 paul 2015-05-16 13:36:26 UTC
On Saturday 16. May 2015 15.19.59 you wrote:
> This file still valid using last digiKam 4.10.0 ?

Sorry, I haven't tested it on anything later than 4.8.4, as I'm still running 
Debian Wheezy. Maybe when I upgrade to Jessie I'll be able to look at 
something recent enough to give feedback.

Thanks for looking into this!

Comment 21 caulier.gilles 2015-05-16 13:38:37 UTC
And with digiKam 4.8 , it still reproducible ?

Gilles Caulier
Comment 22 paul 2015-05-16 15:18:39 UTC
On Saturday 16. May 2015 15.38.37 you wrote:
> And with digiKam 4.8 , it still reproducible ?

Yes. Turn off the "Embedded preview loads full-sized images" option and the 
pixelated output occurs, even when viewing pictures individually in the album 
at 100%.

Comment 23 caulier.gilles 2015-06-25 08:55:58 UTC
New digiKam 4.11.0 is available :


Can you reproduce the problem with this release ?
Comment 24 caulier.gilles 2015-08-17 11:27:56 UTC
digiKam 4.12.0 is out :


We need a fresh feedback using this release please...
Thanks in advance.

Gilles Caulier
Comment 25 caulier.gilles 2016-07-15 20:51:13 UTC
With digiKam 5.0.0, this problem is not reproducible.
I close this file now. Don't hesitate to re-open if necessary.
Gilles Caulier
Comment 26 JF JOLIMAITRE 2017-06-03 12:51:15 UTC
I'm surprised this problem is considered solver. I encounter this (low resolution output when "Embedded preview loads full-sized images" is not selected), both on DK 4.14 and 5.5.