Ofnuts, Qt GMic, just another possiblity to solve the problem
Another possibility to get rid of the lines on the drawing :
- copy the drawing on 3 layers
- make layer 2 50% tranparent (= middle layer)
- make layer 3 33% tranparent (= top layer)
- move layer 2 2 pixels to the left
- move layer 3 2 pixels to the right
- flatten the image
- use 'Colours / Brightness-Contrast' on the result to get more powerful colors
PS : there are still lines on the rear window of the blue bug, use the blur or the smudge tool to get rid of them
Another possibility to get rid of the lines on the drawing :
- copy the drawing on 3 layers
- make layer 2 50% tranparent (= middle layer)
- make layer 3 33% tranparent (= top layer)
- move layer 2 2 pixels to the left
- move layer 3 2 pixels to the right
- flatten the image
- use 'Colours / Brightness-Contrast' on the result to get more powerful colors
PS : there are still lines on the rear window of the blue bug, use the blur or the smudge tool to get rid of them