Northern Kentucky University
convert -crop 100x200+30+20 recent.tif recent.jpg
chops out a rectangle 100x200 (taller than wide, in pixels), displaced 30 in
the x direction and 20 in the y direction, measured from the top left.
It may just be a guessing game to figure out the appropriate values of height,
width, x shift, and y shift. Some browsers indicate the size of the image (if
you choose the 'view image' option).