def test_alpha_composite(self):
# https://stackoverflow.com/questions/3374878
# Arrange
from PIL2 import ImageDraw
expected_colors = sorted([
(1122, (128, 127, 0, 255)),
(1089, (0, 255, 0, 255)),
(3300, (255, 0, 0, 255)),
(1156, (170, 85, 0, 192)),
(1122, (0, 255, 0, 128)),
(1122, (255, 0, 0, 128)),
(1089, (0, 255, 0, 0))])
dst = Image.new('RGBA', size=(100, 100), color=(0, 255, 0, 255))
draw = ImageDraw.Draw(dst)
draw.rectangle((0, 33, 100, 66), fill=(0, 255, 0, 128))
draw.rectangle((0, 67, 100, 100), fill=(0, 255, 0, 0))
src = Image.new('RGBA', size=(100, 100), color=(255, 0, 0, 255))
draw = ImageDraw.Draw(src)
draw.rectangle((33, 0, 66, 100), fill=(255, 0, 0, 128))
draw.rectangle((67, 0, 100, 100), fill=(255, 0, 0, 0))
# Act
img = Image.alpha_composite(dst, src)
# Assert
img_colors = sorted(img.getcolors())
self.assertEqual(img_colors, expected_colors)
def test_alpha_inplace(self):
src = Image.new('RGBA', (128, 128), 'blue')
over = Image.new('RGBA', (128, 128), 'red')
mask = hopper('L')
over.putalpha(mask)
target = Image.alpha_composite(src, over)
# basic
full = src.copy()
full.alpha_composite(over)
self.assert_image_equal(full, target)
# with offset down to right
offset = src.copy()
offset.alpha_composite(over, (64, 64))
self.assert_image_equal(offset.crop((64, 64, 127, 127)),
target.crop((0, 0, 63, 63)))
self.assertEqual(offset.size, (128, 128))
# offset and crop
box = src.copy()
box.alpha_composite(over, (64, 64), (0, 0, 32, 32))
self.assert_image_equal(box.crop((64, 64, 96, 96)),
target.crop((0, 0, 32, 32)))
self.assert_image_equal(box.crop((96, 96, 128, 128)),
src.crop((0, 0, 32, 32)))
self.assertEqual(box.size, (128, 128))
# source point
source = src.copy()
source.alpha_composite(over, (32, 32), (32, 32, 96, 96))
self.assert_image_equal(source.crop((32, 32, 96, 96)),
target.crop((32, 32, 96, 96)))
self.assertEqual(source.size, (128, 128))
# errors
self.assertRaises(ValueError,
source.alpha_composite, over, "invalid source")
self.assertRaises(ValueError,
source.alpha_composite, over, (0, 0),
"invalid destination")
self.assertRaises(ValueError,
source.alpha_composite, over, (0))
self.assertRaises(ValueError,
source.alpha_composite, over, (0, 0), (0))
self.assertRaises(ValueError,
source.alpha_composite, over, (0, -1))
self.assertRaises(ValueError,
source.alpha_composite, over, (0, 0), (0, -1))
