Compose front and back over alpha image

convert ... -compose blend  -define compose:args=50,50 -composite ...

The operator “-mask” takes an external image to be linked to the images in memory. The ‘plus’ form of the operator “+mask” removes the mask from the image.

-read-mask filename

This the same as using a mask used for composite masking operations, with grayscale values causing blended updates of the image the mask is attached to.

Use +read-mask to remove the mask from images.

Real world example

that actually works

convert front.png back.png -mask alpha.png -composite out.png
# or
composite front.png back.png alpha.png out2.png

and as usually I had to guess that.


gm composite front.png back.png alpha.png out3.png