is_equal : throwing an exception claiming image sizes are different, but they arent

[TeddyTeddy]

imgcompare.is_equal($expected_icon_full_path, $observed_icon_full_path, tolerance=2.5)' failed: ImageCompareException: different image sizes, can only compare same size images: A=(16, 16) B=(20, 20)

Both images have 20x20 , verified by command line command "file"