#!/usr/bin/env python
##########################################################################
#
+# Copyright 2011 Jose Fonseca
# Copyright 2008-2009 VMware, Inc.
# All Rights Reserved.
#
##########################################################################/
+'''Snapshot (image) comparison script.
+'''
+
+
import sys
import os.path
-import subprocess
import optparse
+import math
+import operator
-import Image
+from PIL import Image
+from PIL import ImageChops
+from PIL import ImageEnhance
thumb_size = 320, 320
-def compare(im, ref):
- import ImageMath
- # See http://www.pythonware.com/library/pil/handbook/imagemath.htm
- mask = ImageMath.eval("min(abs(a - b), 1)", a=im, b=ref)
- gray = ref.convert('L')
- # TODO
+class Comparer:
+ '''Image comparer.'''
+
+ def __init__(self, ref_image, src_image, alpha = False):
+ self.ref_im = Image.open(ref_image)
+ self.src_im = Image.open(src_image)
+
+ # Ignore
+ if not alpha:
+ self.ref_im = self.ref_im.convert('RGB')
+ self.src_im = self.src_im.convert('RGB')
+
+ self.diff = ImageChops.difference(self.src_im, self.ref_im)
+
+ def write_diff(self, diff_image, fuzz = 0.05):
+ # make a difference image similar to ImageMagick's compare utility
+ mask = ImageEnhance.Brightness(self.diff).enhance(1.0/fuzz)
+ mask = mask.convert('L')
+
+ lowlight = Image.new('RGB', self.src_im.size, (0xff, 0xff, 0xff))
+ highlight = Image.new('RGB', self.src_im.size, (0xf1, 0x00, 0x1e))
+ diff_im = Image.composite(highlight, lowlight, mask)
+
+ diff_im = Image.blend(self.src_im, diff_im, 0xcc/255.0)
+ diff_im.save(diff_image)
+
+ def precision(self):
+ # See also http://effbot.org/zone/pil-comparing-images.htm
+ h = self.diff.histogram()
+ square_error = 0
+ for i in range(1, 256):
+ square_error += sum(h[i : 3*256: 256])*i*i
+ rel_error = float(square_error*2 + 1) / float(self.diff.size[0]*self.diff.size[1]*3*255*255*2)
+ bits = -math.log(rel_error)/math.log(2.0)
+ return bits
+
+ def ae(self):
+ # Compute absolute error
+ # TODO: this is approximate due to the grayscale conversion
+ h = self.diff.convert('L').histogram()
+ ae = sum(h[int(255 * fuzz) + 1 : 256])
+ return ae
def surface(html, image):
def main():
+ global options
+
optparser = optparse.OptionParser(
usage="\n\t%prog [options] <ref_prefix> <src_prefix>",
version="%%prog")
optparser.add_option(
'-o', '--output', metavar='FILE',
- type="string", dest="output",
- help="output filename [stdout]")
+ type="string", dest="output", default='index.html',
+ help="output filename [default: %default]")
optparser.add_option(
'-f', '--fuzz',
- type="string", dest="fuzz", default='5%',
- help="fuzz [default: %default]")
+ type="float", dest="fuzz", default=0.05,
+ help="fuzz ratio [default: %default]")
+ optparser.add_option(
+ '--overwrite',
+ action="store_true", dest="overwrite", default=False,
+ help="overwrite")
(options, args) = optparser.parse_args(sys.argv[1:])
root, ext = os.path.splitext(src_image)
delta_image = "%s.diff.png" % (root, )
if os.path.exists(ref_image) and os.path.exists(src_image):
- if not os.path.exists(delta_image) \
+ if options.overwrite \
+ or not os.path.exists(delta_image) \
or (os.path.getmtime(delta_image) < os.path.getmtime(ref_image) \
and os.path.getmtime(delta_image) < os.path.getmtime(src_image)):
- subprocess.call(["compare", '-metric', 'AE', '-fuzz', options.fuzz, ref_image, src_image, delta_image])
+
+ comparer = Comparer(ref_image, src_image)
+ comparer.write_diff(delta_image, fuzz=options.fuzz)
html.write(' <tr>\n')
surface(html, ref_image)