Pygame change image colour but preserve transparency-CodePudding

I've got a function that takes an image and adjusts all of the RGB values by a given amount:

def colour(self,img,col):
    img = self.my_image.copy()
    col = (col[0],col[1],col[2],0)
    img.fill(col, None, pygame.BLEND_RGBA_ADD)
    return img

I want to apply this to a partially transparent image. But when I apply this to the image, the transparent pixels become coloured. I want these pixels to stay transparent, but any opaque pixels to be coloured as normal. Is there any way I can do this, without having to loop through every pixel and check if each one is transparent before adjusting it? Thanks

CodePudding user response：

fill treats the color to be solid. You have to use blit. Create a transparent image the size of the source image and fill it with the color. Finally, mix both images:

def colour(self, img, col):
    img = self.my_image.copy()
    color_img = pygame.Surface(img.get_size(), pygame.SRCALPHA)
    color_img.fill((col[0], col[1], col[2], 0))
    img.blit(color_img, (0, 0), special_flags = pygame.BLEND_RGBA_ADD)
    return img