itch.io

Looks like you have a typo of ':' instead of '.' in your grayscale import script. Try this:

on click do
 # make 1-bit dithered image
 i:read["image" "gray"]
 r:image[c.size]
 r.paste[i 0,0,r.size]
 r.transform["dither"]
 c.paste[r]
end

Sometimes it's helpful to try things step-by-step in the Listener when they don't seem to work properly:

As for image export, you're only copying from the card's background image, which does not include the contents of any canvases stacked on top:

on click do
 write[card.image.copy[c.pos c.size]]
end

If you want to export the image, you need to "copy[]" from the canvas:

on click do
 write[c.copy[]]
end

And as in the examples for The Ornamented Ovum, you may want to map pattern 0 (transparent) to pattern 32 (opaque white) before exporting:

on click do
 write[c.copy[].map[0 dict 32]]
end