[pygame] Surface.blit() BLEND_ADD vs. BLEND_RGBA_ADD

[Florian Berger <fberger@xxxxxxxxxxxxxxxxx>]

Hi,

I am toying around with the above blitting flags. I am blitting a RGBA
sprite surrounded by transparent (i.e. alpha) pixels on a solid RGBA
surface (at least I suppose it is so, both are created from RGBA PNG
images).

In my test setup, there is no difference between BLEND_ADD and
BLEND_RGBA_ADD. I hoped that the latter would honor alpha transparency,
and not add color values of transparent pixels, but this seems not to
be the case. :-/

Has anyone played with this? What is the difference between these two
supposed to be?

Thanks!
        Florian