Please, always provide your IM version and platform when asking questions, since syntax may differ. If you are on a Unix like system, then see my script, multicrop2, at my link below. Is that what you are trying to do? If not, post your input image to some free hosting service such as dropbox.com ...
I have an image.png with multiple rectangles, each one surrounded by transparency. All different width/heights. I created a mask using: convert image.png -alpha extract mask.png So the transparency area is all black and the images are all white. Now what I would like to do is extract from image.png ...