scripts/snapdiff.py

#!/usr/bin/env python
##########################################################################
#
# Copyright 2011 Jose Fonseca
# Copyright 2008-2009 VMware, Inc.
# All Rights Reserved.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
##########################################################################/


'''Snapshot (image) comparison script.
'''


import sys
import os.path
import optparse
import math
import operator

from PIL import Image
from PIL import ImageChops
from PIL import ImageEnhance
from PIL import ImageFilter


thumb_size = 320, 320

gaussian_kernel = ImageFilter.Kernel((3, 3), [1, 2, 1, 2, 4, 2, 1, 2, 1], 16)

class Comparer:
    '''Image comparer.'''

    def __init__(self, ref_image, src_image, alpha = False):
        if isinstance(ref_image, basestring):
            self.ref_im = Image.open(ref_image)
        else:
            self.ref_im = ref_image

        if isinstance(src_image, basestring):
            self.src_im = Image.open(src_image)
        else:
            self.src_im = 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 size_mismatch(self):
        return self.ref_im.size != self.src_im.size

    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, filter=False):
        if self.size_mismatch():
            return 0.0

        diff = self.diff
        if filter:
            diff = diff.filter(gaussian_kernel)

        # See also http://effbot.org/zone/pil-comparing-images.htm
        h = 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, fuzz = 0.05):
        # Compute absolute error

        if self.size_mismatch():
            return sys.maxint

        # 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):
    if True:
        name, ext = os.path.splitext(image)
        thumb = name + '.thumb' + ext
        if os.path.exists(image) \
           and (not os.path.exists(thumb) \
                or os.path.getmtime(thumb) < os.path.getmtime(image)):
            im = Image.open(image)
            im.thumbnail(thumb_size)
            im.save(thumb)
    else:
        thumb = image
    html.write('        <td><a href="%s"><img src="%s"/></a></td>\n' % (image, thumb))


def is_image(path):
    name = os.path.basename(path)
    name, ext1 = os.path.splitext(name)
    name, ext2 = os.path.splitext(name)
    return ext1 in ('.png', '.bmp') and ext2 not in ('.diff', '.thumb')


def find_images(prefix):
    prefix = os.path.abspath(prefix)
    if os.path.isdir(prefix):
        prefix_dir = prefix
    else:
        prefix_dir = os.path.dirname(prefix)

    images = []
    for dirname, dirnames, filenames in os.walk(prefix_dir, followlinks=True):
        for filename in filenames:
            filepath = os.path.join(dirname, filename)
            if filepath.startswith(prefix) and is_image(filepath):
                images.append(filepath[len(prefix):])

    return images


def main():
    global options

    optparser = optparse.OptionParser(
        usage="\n\t%prog [options] <ref_prefix> <src_prefix>")
    optparser.add_option(
        '-o', '--output', metavar='FILE',
        type="string", dest="output", default='index.html',
        help="output filename [default: %default]")
    optparser.add_option(
        '-f', '--fuzz',
        type="float", dest="fuzz", default=0.05,
        help="fuzz ratio [default: %default]")
    optparser.add_option(
        '-a', '--alpha',
        action="store_true", dest="alpha", default=False,
        help="take alpha channel in consideration")
    optparser.add_option(
        '--overwrite',
        action="store_true", dest="overwrite", default=False,
        help="overwrite images")

    (options, args) = optparser.parse_args(sys.argv[1:])

    if len(args) != 2:
        optparser.error('incorrect number of arguments')

    ref_prefix = args[0]
    src_prefix = args[1]

    ref_images = find_images(ref_prefix)
    src_images = find_images(src_prefix)
    images = list(set(ref_images).intersection(set(src_images)))
    images.sort()

    if options.output:
        html = open(options.output, 'wt')
    else:
        html = sys.stdout
    html.write('<html>\n')
    html.write('  <body>\n')
    html.write('    <table border="1">\n')
    html.write('      <tr><th>%s</th><th>%s</th><th>&Delta;</th></tr>\n' % (ref_prefix, src_prefix))
    for image in images:
        ref_image = ref_prefix + image
        src_image = src_prefix + image
        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 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)):

                comparer = Comparer(ref_image, src_image, options.alpha)
                comparer.write_diff(delta_image, fuzz=options.fuzz)

            html.write('      <tr>\n')
            surface(html, ref_image)
            surface(html, src_image)
            surface(html, delta_image)
            html.write('      </tr>\n')
            html.flush()
    html.write('    </table>\n')
    html.write('  </body>\n')
    html.write('</html>\n')


if __name__ == '__main__':
    main()