This looks like you need to convert the 1 plane left input to
chromakey in your patch to a 4 plane matrix so that you can composite
in ARGB (otherwise you're just compositing the binary image with the
alpha channel, which is all white). Try inserting a jit.matrix 4 char
320 240 between cv.jit.binedge and jit.chromakey.
From the sound of what you want to do, it seems like you might want
to look at the jit.chromakey-3sources.pat example, using your binary
image as the alpha channel (don't even need chromakey here, if this
is the case, you can just use the output o cv.jit.binedge as the
alpha mask for jit.alphablend).