Question

I’ve just started working with pygame and I’m trying to make a semi-transparent sprite, and the sprite’s source file is a non-transparent bitmap file loaded from the disk. I don’t want to edit the source image if I can help it. I’m sure there’s a way to do this with pygame code, but Google is of no help to me.

Answer 1

I may have not been clear in my original question, but I think I figured it out on my own. What I was looking for turns out to be Surface’s set_alpha() method, so all I had to do was make sure that translucent images were on their own surface.

Here’s an example with my stripped down code:

import pygame, os.path
from pygame.locals import *

class TranslucentSprite(pygame.sprite.Sprite):
  def __init__(self):
    pygame.sprite.Sprite.__init__(self, TranslucentSprite.container)
    self.image = pygame.image.load(os.path.join('data', 'image.bmp'))
    self.image = self.image.convert()
    self.image.set_colorkey(-1, RLEACCEL)
    self.rect = self.image.get_rect()
    self.rect.center = (320,240)

def main():
  pygame.init()
  screen = pygame.display.set_mode((640,480))
  background = pygame.Surface(screen.get_size())
  background = background.convert()
  background.fill((250,250,250))
  clock = pygame.time.Clock()
  transgroups = pygame.sprite.Group()
  TranslucentSprite.container = transgroups

  """Here's the Translucency Code"""
  transsurface = pygame.display.set_mode(screen.get_size())
  transsurface = transsurface.convert(screen)
  transsurface.fill((255,0,255))
  transsurface.set_colorkey((255,0,255))
  transsurface.set_alpha(50)

  TranslucentSprite()
  while 1:
    clock.tick(60)
    for event in pygame.event.get():
      if event.type == QUIT:
        return
      elif event.type == KEYDOWN and event.key == K_ESCAPE:
        return
    transgroups.draw(transsurface)
    screen.blit(background,(0,0))
    screen.blit(transsurface,(0,0))
    pygame.display.flip()

if __name__ == '__main__' : main()

Is this the best technique? It seems to be the most simple and straightforward.