...rt.

I tested with the x64 3.0.90 test build and latest daily development build for Windows. The GMIC settings were Colorize interactive with the input set to Lineart and the output set to Image+Colors (2 layers). First off the output from Krita was Colors+Image which was kind of weird but not the main problem. The real bug is that the GMIC implementation in Krita bleeds the colors through aliased strokes which messes up the borders.

Here are some images: http://imgur.com/a/6JGQ2

The first image isn't really black, it's a .png with a bunch of overlapping circles with an alpha channel. The second image is the output from GMIC in gimp, which looks good and clean. The third image is from the GMIC in Krita. The colors are not exactly the same but it shouldn't matter. If you zoom in you should be able to see some artifacts like the pink color bleeding through to the green area. If you save the image and zoom in even more you should be able to see lots of pink jaggies along the green+lineart edge which looks pretty bad, and this is still with a pretty hard brush and big strokes (20px or so). With real lineart it would probably look a lot worse.

I think the issue has to do with the antialiasing of the strokes. In GIMP, looking at the green+lineart edge, if you disable the lineart layer you can see that the coloring layer seems to move to the left because it's only being applied behind pure black pixels. However if you do the same thing in Krita you can see that the layer doesn't seem to move and that it is actually being applied to gray (antialiased pixels) as well which looks bad.

Can anyone else reproduce this issue?

Edit: The comic colorize GMIC filter seems to work better.