PMC Editing Wiki: Tools GraphicsMagick
2021-12-26
Command is -fill RGB_DESTINATION -opaque RGB_SOURCE.
This example replaces 255,255,255 (white) with 0,0,0 (black):
rem vte_grass gm convert source.png -fill "rgb(0, 0, 0)" -opaque "rgb(255, 255, 255)" destination.bmp
However if your source image has transparent background and you do -opaque “rgb(0, 0, 0)” it will use the transparent background. GraphicsMagick thinks RGB 0,0,0 is transparent ;)