Blurring in PyGame

I'm working on a short intro in PyGame, and I need to blur some static lines. After two days of searching, I can't find anything.

Does PyGame have a built-in method to blur a shape or surface? Will I need to do it manually? What would be the best way to approach this?

To clarify, I'm not looking for motion blur – I just need a simple in-place blur, almost like a glowing effect.

Solution

2023 update: If you're using pygame-ce, the functions pygame.transform.box_blur and pygame.transform.gaussian_blur were added in the 2.2.0 release.

There's no built-in way to blur a Surface.

Workarounds are:

scale the Surface with pygame.transform.smoothscale and then back to its original size (ugly)
iterating over each pixel, get the color of the neighbour pixels, calculate the average value for red, green, and blue, and set the color of that pixel (slow as hell if not using something like numpy)

I recommend using the Python Imaging Library (PIL), since it's nice and fast.

Here's a simple and running example:

import pygame
from PIL import Image, ImageFilter

pygame.init()
screen = pygame.display.set_mode((512, 512))
clock = pygame.time.Clock()

compressed = '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'
size, image_mode, raw = (128, 128), 'RGBA', compressed.decode("base64").decode("zlib")

# create the original pygame surface
surf = pygame.image.fromstring(raw, size, image_mode)

# create a PIL image and blur it
pil_blured = Image.fromstring("RGBA", size, raw).filter(ImageFilter.GaussianBlur(radius=6))

# convert it back to a pygame surface
other = pygame.image.fromstring(pil_blured.tostring("raw", image_mode), size, image_mode)

pygame.time.set_timer(pygame.USEREVENT, 1000)

while True:
    for e in pygame.event.get():
        if e.type == pygame.USEREVENT: surf, other = other, surf
        if e.type == pygame.QUIT: break
    else:
        screen.fill((255, 255, 255))
        screen.blit(surf, (192, 192))
        pygame.display.flip()
        clock.tick(60)
        continue
    break

enter image description here

Hint: If you're on Windows and want to install PIL, download it from here and install it via

pip install Pillow-2.8.2-cp27-none-win32.whl

or whatever version you downloaded (installing PIL on Windows can be a great PITA otherwise).