crop

crop/<width>x<height>+<x>+<y>

Cuts a region out of the image. The offset is measured from the top left.

crop/100x100+10+20     100 by 100, starting 10 across and 20 down
crop/100x100           100 by 100 from the centre
crop/50%x50%+0+0       the top left quarter

A region larger than the image is reduced to fit. An offset outside the image produces an empty result.

Some clients escape a + as %20, which arrives as a space. crop converts a space back to a +, so 100x100%20350%200 works.