def _apply_postprocessing(self, image, user):
size = image.size
alpha = 220
alphaf = alpha / 255.0
stops = [
(2.0, image_utils.parse_rgb(user.color_primary, alpha), image_utils.parse_rgb(user.color_secondary, alpha))
]
bg = image.convert("L").convert("RGB")
fg = image_utils.get_gradient_image(size, stops)
# combine bg and fg layers via screen blend mode with 75% opacity on fg layer
# see this wikipedia article for a description of screen blend mode:
# http://en.wikipedia.org/wiki/Blend_modes
output = Image.new("RGB", size)
data = []
blend_func = lambda b, f: image_utils.clamp(255.0 - (((255.0 - alphaf * f) * (255.0 - b)) / 255.0))
for y in xrange(size[1]):
for x in xrange(size[0]):
pos = (x, y)
bg_px = bg.getpixel(pos)
fg_px = fg.getpixel(pos)
color = tuple(blend_func(bg_px[i], fg_px[i]) for i in xrange(len(bg_px)))
data.append(color)
output.putdata(data)
return output
def create_gradient(width, height, user):
alpha = 255
stops = [(
2.0,
image_utils.parse_rgb(user.color_primary, alpha),
image_utils.parse_rgb(user.color_secondary, alpha)
)]
return image_utils.get_gradient_image((width, height), stops)
