Also, I guess the docs should be updated to specify which blend operations the flags do exactly.
On Fri, Apr 18, 2008 at 10:49 AM, Lenard Lindstrom <[EMAIL PROTECTED]> wrote: > Brian Fisher wrote: > > > > On Thu, Apr 17, 2008 at 10:41 AM, Lenard Lindstrom <[EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]>> wrote: > > > > For alpha surfaces a blend may be useful for doing shadow effects. > > Such effects require extracting and altering the alpha plane. Want > > to make a shadow for antialiased text. Extract the alpha and apply > > to an all black surface. Right now surfarray must be used to do > > this in a practical way. Otherwise it would have to be done > > per-pixel with get_at/set_at. > > > > I'm curious - how exactly would you expect to be able to extract the alpha > channel from a font char and apply it to a black surface using the blit > flags? BLEND_MAX? Is there a technique that would also work for a surface > with arbitrary color values? > > > I was thinking of this: > > text = font.render("....", True, some_color) > alpha = pygame.Surface(text.get_size(), pgyame.SRCALPHA, 32) > alpha.fill((0, 0, 0, 255)) > alpha.blit(text, (0, 0), None, pygame.BLEND_MIN) > > This assumes BLEND_MIN applies to alpha as well. If dA = sA + dA - > ((sA*dA)/255) then a destination color of (0, 0, 0, 0) will work. Source > color is irrelevant. It extras alpha from any image. > > -- > > Lenard Lindstrom > <[EMAIL PROTECTED]> > >
