On Tue, Oct 7, 2008 at 7:18 PM, Yumiko Shirasagi <[EMAIL PROTECTED]>wrote:
> Hello, > > When I blit an image such as this (generated dynamically with PIL, and > saved here by pygame.image.save)- > http://xs432.xs.to/xs432/08412/mask808.png > to this screen, using the line "screen.blit(mask, (0, 0), None, > BLEND_RGBA_SUB)"- > http://xs432.xs.to/xs432/08412/screen136.png > it results in this- > http://xs432.xs.to/xs432/08411/tsukiyo3634.jpg > > Is this what is supposed to happen? It seems to me that BLEND_RGBA_SUB > should respect the the alpha of the surface being blitted and avoid > subtracting the fully transparent gray pixels. Of course an alternate > solution is to get rid of those gray pixels, but I'm wondering whether > it is a bug in pygame, or if there is a solution that doesn't require > altering the way the surface is generated. > a quick test tells that , at pixel level, pygame 1.8.1release: sf1 sf2 sf1.blit(sf2,None,'BLEND_RGBA_SUB') (r1,g1,b1,a1) (r2,g2,b2,a2) (clamp(r1-r2),clamp(g1-g2), clamp(b1-b2), 255) Looks wrong to me, but there are not specs for the oper. -- claxo
