The differences are more evident if you try to open an image in some wide-gamut color space (pro photo, rec.2020, ACEScg…).
Also, try to change the monitor profile and see if the previews in gimp and gmic match.
In gmic, you need to select a filter to activate the color management (I’ll see with @David_Tschumperle how to solve this little issue). For example, you can select “Color → basic adjustments” with all the sliders at zero.
And guess what? You can download the new appimage side-by-side with the previous one, and run alternatively one or the other to check the differences… a very convenient way to test new features!
OK, some news. I got the patch from @Carmelo_DrRaw, and started to work on a clean integration into the G’MIC plug-in source code. I’ve also managed to make the preview display the color-corrected version of the image when no filters are selected. The current GimpPreview widget of the GIMP API is a bit wonky, so this was not a cakewalk. There are probably some bugs remaining, but the code is already available in the current git master, so you are welcome to try compiling it and test it.
Maybe Andrea will have some time to include this version in his AppImage ?
@Carmelo_DrRaw, we would be really interested by any hints to make our new Qt-based plug-in color-managed as well for GIMP 2.9. I don’t get how to modify the code you’ve done for the GTK-based plug-in, to make it work with the Qt-based plug-in.
Basically, what we have is a float* RGB (or RGBA) buffer, and we’d like to modify it in-place to apply the GIMP color profile to the pixels it contains.