for frame_no in range(options.start, options.stop + 1):
ref_image = "%s%04u.png" % (ref_prefix, frame_no)
src_image = "%s%04u.png" % (src_prefix, frame_no)
for frame_no in range(options.start, options.stop + 1):
ref_image = "%s%04u.png" % (ref_prefix, frame_no)
src_image = "%s%04u.png" % (src_prefix, frame_no)