Starting from a layer with mainly 2 colors or a combination of them create an alpha channel using, in the 3D color space, the intersection between the segment from foreground color to background color points and the perpendicular plane passing to each pixel of the layer.
In a layer with mainly 2 colors or a combination of them
from "Colors" menu run "Background to Alpha ..." plugin
use color parameters context menu to import current foreground or background colors if needed and run the script
at the end a new layer named "Background to Alpha" will be created with the same subject of the processed layer but without the background color.
Currently numpy python package is required to compute 3D color space minimum distances.
Copy plug-ins/background_to_alpha.py to ~/.gimp-2.8/plug-ins/ directory.
- remove dependency from numpy python package
- reimplement it using C instead of python