A little command line tool to merge specific channels of multiple images into one RGBA image.
go get github.com/blblblu/rgba-channel-merge
Use the red, green and blue channel from first.png as green blue and red (in that order), and the alpha channel from second.png as alpha channel:
> rgba-channel-merge first.png gbrx second.png xxxa output.png
TODO: more readme...