Changing pixel alpha in textures

I need to be able to alter the alpha channel of a texture. TextureBuffer doesn't work in miniB3D. I tried loading in the texture as a pixmap, and changing from there, but I can't figure out a way to load the pixmap into the texture without first saving the pixmap to the hard drive first.
I noticed that there is a pixmap field in the TTexture type. Would it be safe to access that pixmap and change the alpha channel there?

Yes that should be OK.