Why are my pygame images not getting the alpha set after changing from windows to mac

Question

These are the parts of the code that are relevant:

class t_color(object):
    BLUE = (0, 0, 255)
    GREY = (128, 128, 128)
    GREEN = (0, 128, 0)
    LIME = (0, 255, 0)
    PURPLE = (128, 0, 128)
    RED = (255, 0, 0)
    SILVER = (192, 192, 192)
    WHITE = (255, 255, 255)
    BLACK = (0, 0, 0)
    YELLOW = (255, 255, 0)

IMAGE_ALPHA = t_color.BLACK
...
img = pygame.image.load('images/' + str(i) + '.bmp')
img.set_colorkey(IMAGE_ALPHA)
g.images.append(img)

On windows this was working fine. Now that I'm using Mac (10.9) and python 2.7.5(on windows I had 2.7.6) pygame 1.9.2 (on windows I had 1.9.1)

Here are the images I'm useing, they are only 32x32 px: http://www.mediafire.com/download/nf9exc8trged687/images.zip

I want to set the black to be transparent as the images are BMP files and don't support transparency.

Does anyone know what is causing this or how to fix?

Answer 1

https://stackoverflow.com/a/13078080/3157252 -- Not mine, foudnd it

There's per-pixel alpha, colorkey alpha, and per-surface alpha. You're asking for colorkey.

When you call convert_alpha() it creates a new surface for per-pixel alpha.

And from set_colorkey

The colorkey will be ignored if the Surface is formatted to use per pixel alpha values.

So: Load image with .convert() Since you want to use a color key. Then call set_colorkey.

Also, I saw nothing in the docs about passing "-1" as first argument to set_colorkey.

That's probably from a tutorial, which has a load_image function to grab the topleft pixel's color value.