image_test.py 文件源码

def test_to_string__premultiplied(self):
        """ test to make sure we can export a surface to a premultiplied alpha string
        """

        def convertRGBAtoPremultiplied(surface_to_modify):
            for x in xrange_(surface_to_modify.get_width()):
                for y in xrange_(surface_to_modify.get_height()):
                    color = surface_to_modify.get_at((x, y))
                    premult_color = (color[0]*color[3]/255,
                                     color[1]*color[3]/255,
                                     color[2]*color[3]/255,
                                     color[3])
                    surface_to_modify.set_at((x, y), premult_color)

        test_surface = pygame.Surface((256, 256), pygame.SRCALPHA, 32)
        for x in xrange_(test_surface.get_width()):
            for y in xrange_(test_surface.get_height()):
                i = x + y*test_surface.get_width()
                test_surface.set_at((x,y), ((i*7) % 256, (i*13) % 256, (i*27) % 256, y))
        premultiplied_copy = test_surface.copy()
        convertRGBAtoPremultiplied(premultiplied_copy)
        self.assertPremultipliedAreEqual(pygame.image.tostring(test_surface, "RGBA_PREMULT"),
                                         pygame.image.tostring(premultiplied_copy, "RGBA"),
                                         pygame.image.tostring(test_surface, "RGBA"))
        self.assertPremultipliedAreEqual(pygame.image.tostring(test_surface, "ARGB_PREMULT"),
                                         pygame.image.tostring(premultiplied_copy, "ARGB"),
                                         pygame.image.tostring(test_surface, "ARGB"))

        no_alpha_surface = pygame.Surface((256, 256), 0, 24)
        self.assertRaises(ValueError, pygame.image.tostring, no_alpha_surface, "RGBA_PREMULT")