+def _compare(ref_image, src_image, delta_image):
+ import subprocess
+ p = subprocess.Popen([
+ 'compare',
+ '-metric', 'AE',
+ '-fuzz', '%u%%' % options.fuzz,
+ '-dissimilarity-threshold', '1',
+ ref_image, src_image, delta_image
+ ], stderr=subprocess.PIPE)
+ _, stderr = p.communicate()
+ try:
+ return int(stderr)
+ except ValueError:
+ return 0xffffffff
+
+
+def compare(ref_image, src_image, delta_image):
+ ref_im = Image.open(ref_image)
+ src_im = Image.open(src_image)
+
+ ref_im = ref_im.convert('RGB')
+ src_im = src_im.convert('RGB')
+
+ diff = ImageChops.difference(src_im, ref_im)
+
+ mask = ImageEnhance.Brightness(diff).enhance(100.0/options.fuzz)
+ mask = mask.convert('L')
+
+ lowlight = Image.new('RGB', src_im.size, (0xff, 0xff, 0xff))
+ highlight = Image.new('RGB', src_im.size, (0xf1, 0x00, 0x1e))
+ delta_im = Image.composite(highlight, lowlight, mask)
+
+ delta_im = Image.blend(src_im, delta_im, 0xcc/255.0)
+ delta_im.save(delta_image)
+
+ # See also http://effbot.org/zone/pil-comparing-images.htm
+ # TODO: this is approximate due to the grayscale conversion
+ h = diff.convert('L').histogram()
+ ae = sum(h[255 * options.fuzz // 100 + 1 : 256])
+ return ae