Remove the colourPassed
Make a black and white version of hopper.png called bw.png.
deft image grayscale hopper.png -o bw.png
Input
hopper.png 29.9 KB · 128x128

Output
bw.png 10.7 KB · 128x128

Automatic checks (1)
- grayscale: file = "bw.png", gray = true