Randomly remove pixels from an image

[drmarie]

I'd like to take an image and randomly remove 75% of the pixels. Can this be done?

[fmw42]

what do you mean by "remove"? Do you mean make them transparent?

[drmarie]

Yes

[fmw42]

try


convert yourimage \
\( -size 128x128 xc: +noise random -channel red -separate \
+channel -threshold 75% -transparent black \) \
-alpha off -compose copy_opacity -composite resultimage.png

The command creates a mask image of random noise in the red channel, then thresholds it so that 25% is white and 75% is black, then makes the 75% black into transparency, then puts the mask into the alpha channel of the resulting image so that 75% is transparent and 25% is the original image.