meillo@0: TODO:
meillo@0: 
meillo@0: - security checks
meillo@24: 
meillo@5: - verify that input files are images
meillo@47: 	mogrify doesnt always return an error code if it is no supported image type
meillo@24: 	so is the problem with gimp's xcf format
meillo@47: 	(is that solvable in any case??)