(Aug 26, 2011 11:51 AM)ThemsAllTook Wrote:  Aha, you've hit another classic problem. Short version: Your texture appears to be using premultiplied alpha; use glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA) and the black halo should disappear.

Thanks! That solved it.

(Aug 26, 2011 11:51 AM)ThemsAllTook Wrote:  As for why your pixels are premultiplied, I presume you're loading the texture with UIImage or some other Apple API? Apple's image loading functions will typically premultiply your data for you, though in some cases you can disable it. If you want to load the image without premultiplying, you can (maybe? haven't done it in a while) change the options you use to load the image, or use libpng directly.

Yeah, I'm using UIImage CGBitmapContext. (Everything is copied and pasted from here)
Should I bother with it? Why do I care if my images are premultiplied if they are shown correctly? What are the benefits?

One last question which is probably more related to my previous thread-
If I manually sort my objects/sprites by depth, and then call glDrawWhatever in that order, can I ditch depth test and the depth buffer?