Detecting dark images in scanned pdf's

[MMM]

Hi,

i'm printing quite a lot and wondered if there's a script way to identify dark contiguous areas, esp. black image/illustration backgrounds and distinguish them from text in order to save toner by selectively adjusting levels ...

Thanks!

[anthony]

convert the imge to greyscale (as a precaution) then look at the averge color of the image.
scanned text should have a very high (lots of white) value. Images with dark areas should stand out very well.

If you want to locate patches of dark color, I would blur the image and then do a 'fuzzy trim' with a 'white seeding color (add a white border as a starting point for trim) and see if you get anything.

See Trimming Noisy images
http://www.imagemagick.org/Usage/crop/#trim_noisy

[MMM]

Thanks. I've also found viewtopic.php?f=1&t=8331. Shadow/Highlights might work too.