Support dark theme

[suamor]

I have not completely tested it, but I saw that dark theme on Ubuntu does not look very well on Canorus. Possibly find out if Canorus is running on a dark theme and adjust interface to it.

If Qt has no direct properties for that we could try to find out if the background color of the window is "dark".

So far I noticed that the editor window is white which is a very strong contrast to the black and might hurt eyes on some displays.

[matevz]

For editor you can already setup custom colors in the Settings dialog. Saving and loading of colors (with some predefined themes?) would be nice, yeah (maybe a similar mechanism to saving/loading keyboard shortcuts?). Also, toolbars need to get dark theme (Qt should help here) and icons need to be rebrushed to white. Maybe we could automate icons conversion somehow?

[suamor]

Yes, Imagemagick does a good job in this. You may need additional tools to use it depending on format or operation you perform on the image:
https://imagemagick.org/script/formats.php

[matevz]

Yes, Imagemagick does a good job in this.

Does it work on SVG as well?