Pillow/Tests/test_image_quantize.py

from .helper import PillowTestCase, hopper

from PIL import Image


class TestImageQuantize(PillowTestCase):

    def test_sanity(self):
        image = hopper()
        converted = image.quantize()
        self.assert_image(converted, 'P', converted.size)
        self.assert_image_similar(converted.convert('RGB'), image, 10)

        image = hopper()
        converted = image.quantize(palette=hopper('P'))
        self.assert_image(converted, 'P', converted.size)
        self.assert_image_similar(converted.convert('RGB'), image, 60)

    def test_libimagequant_quantize(self):
        image = hopper()
        try:
            converted = image.quantize(100, Image.LIBIMAGEQUANT)
        except ValueError as ex:
            if 'dependency' in str(ex).lower():
                self.skipTest('libimagequant support not available')
            else:
                raise
        self.assert_image(converted, 'P', converted.size)
        self.assert_image_similar(converted.convert('RGB'), image, 15)
        self.assertEqual(len(converted.getcolors()), 100)

    def test_octree_quantize(self):
        image = hopper()
        converted = image.quantize(100, Image.FASTOCTREE)
        self.assert_image(converted, 'P', converted.size)
        self.assert_image_similar(converted.convert('RGB'), image, 20)
        self.assertEqual(len(converted.getcolors()), 100)

    def test_rgba_quantize(self):
        image = hopper('RGBA')
        self.assertRaises(ValueError, image.quantize, method=0)

        self.assertEqual(image.quantize().convert().mode, "RGBA")

    def test_quantize(self):
        image = Image.open('Tests/images/caption_6_33_22.png').convert('RGB')
        converted = image.quantize()
        self.assert_image(converted, 'P', converted.size)
        self.assert_image_similar(converted.convert('RGB'), image, 1)

    def test_quantize_no_dither(self):
        image = hopper()
        palette = Image.open('Tests/images/caption_6_33_22.png').convert('P')

        converted = image.quantize(dither=0, palette=palette)
        self.assert_image(converted, 'P', converted.size)

    def test_quantize_dither_diff(self):
        image = hopper()
        palette = Image.open('Tests/images/caption_6_33_22.png').convert('P')

        dither = image.quantize(dither=1, palette=palette)
        nodither = image.quantize(dither=0, palette=palette)

        self.assertNotEqual(dither.tobytes(), nodither.tobytes())