pyopengl-users

[PyOpenGL-Users] problems with transparency

[altern <al...@gm...>]

hi

i am trying to get transparency with some png images that have alpha 
channel. But i just get to see the alpha channel itself. I mean i get 
the transparency but the image is black, like all colors but the 
transparency have been deleted.

I am importing the images with pygame like this

surface = pygame.image.load(path)
if surface.get_alpha is None:
	surface = surface.convert()
else:
	surface = surface.convert_alpha()

bin = pygame.image.tostring(surface, "RGBA", 1)
w, h = surface.get_width(), surface.get_height()

textid = glGenTextures(1)
glBindTexture(GL_TEXTURE_2D, textid)

gluBuild2DMipmaps(GL_TEXTURE_2D, 4, w, h, GL_RGBA, GL_UNSIGNED_BYTE, bin)

glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_BLEND)

glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP)

glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST)

any ideas?

thanks


enrike

Re: [PyOpenGL-Users] problems with transparency

[Erik J. <ejo...@fa...>]

On Tue, 26 Sep 2006 21:02:04 +0200, "altern" <al...@gm...> said:
> hi
> 
> i am trying to get transparency with some png images that have alpha 
> channel. But i just get to see the alpha channel itself. I mean i get 
> the transparency but the image is black, like all colors but the 
> transparency have been deleted.

That's a strange problem.  Do you have something like:
 glEnable(GL_TEXTURE_2D)
 glEnable(GL_BLEND);
 glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)

in your initialization?

Another thing you could try is replacing:
gluBuild2DMipmaps(GL_TEXTURE_2D, 4, w, h, GL_RGBA, GL_UNSIGNED_BYTE,
bin)

with:
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA,
GL_UNSIGNED_BYTE, bin)

I've used mipmaps in the past, but I don't have the code readily
available.

if you are still having problems, you could look at this:
http://disruption.ca/gutil/example2/example2a.html

Erik