Thumbnails not color-managed + severely distorted shadow tonality for thumbs, previews

Elle Stone ellestone at
Thu Nov 16 13:00:14 GMT 2017

On 11/15/2017 06:03 PM, Elle Stone wrote:
> Do I need to install a more recent version of boost? 1.63 and 1.65 are
> both available from Gentoo Portage.

Installing boost 1.63 allowed digiKam from git to compile without any 

On 11/15/2017 04:38 PM, Elle Stone wrote:
> I downloaded the digiKam source code from 
> and modified core/libs/dimg/filters/icc/icctransform.cpp line 58 from
> transformFlags = 0;
> to
> transformFlags = cmsFLAGS_NOOPTIMIZE;

Yes, changing the transformFlags to always include cmsFLAGS_NOOPTIMIZE 
makes the shadow tonality for previews match GIMP-2.9's shadow tonality.

For actual use in digiKam, if the decision is made to allow not using 
the optimizations - which really does seem necessary for proper display 
of linear gamma images - there would probably also need to be a user 
option in the digiKam color management settings - perhaps similar to 
what Krita has - to use or not use the optimizations. Apparently not 
using the optimizations can lead to slower display and conversion of 
images, depending on the type of conversion and the type of monitor 
profile and etc.

Also in the version of digiKam that I installed from git, the thumbnails 
are color-managed. Of course the shadows are still posterized from being 
linear gamma 8-bit thumbnails, but that is to be expected.

There is one more variable (setting or not setting the system monitor 
profile) that I want to double-check, that might affect the display of 
the thumbnails: When using the version of digiKam from Gentoo Portage, I 
had set the system monitor profile upon starting X. But this morning, 
testing my modified "git" version of digiKam, I also unset the system 
monitor profile and set the digiKam monitor profile from disk, so that 
the digiKam color management settings and GIMP/Krita color management 
settings would match as closely as possible. I can't imagine how this 
would affect display of thumbnails but not the previews, but maybe it 
somehow does.

Unfortunately (a small and basically irrelevant aside), my compiled 
version of digiKam doesn't show an icon in the task bar, so when 
minimized to the task bar tray it almost seems like digiKam isn't 
running any more, but it really is.

On 11/15/2017 03:48 PM, Maik Qualmann wrote:
> Can you provide a image to test the color management?

I made a 16-bit integer png test image. At 1200x1200, the file is 
2.8MiB, resized to 1024x1024, it's 1.9MiB - I can resize the image to be 
smaller, if that would be better. Let me know what size you want and 
I'll upload the image.


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