Im using the Texture2D functions from Touchfighter sample app.
I want to place a string on my OpenGL view, and have created one using the initWithString initializer.
Although i can change the foreground color easily enough using glColor4f, i always get a black background. The Touch example is transparent, and i've hacked my code to mimic the touch implementation but still cant seem to get the background transparent. All my other textures seem to have a perfectly working alpha channel. I've even tried different blend functions for the text.

Any ideas?
texture = [[Texture2D alloc] initWithString:@"Hello" dimensions:CGSizeMake(32., 16.) alignment:UITextAlignmentLeft font:[UIFont systemFontOfSize:14.0]];

glEnable(GL_TEXTURE_2D);
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glEnable(GL_BLEND);
[texture drawAtPoint:CGPointMake(0,0)];

I made some progress, but still can't get this right.

I've found that with a blendfunction of (GL_ONE, GL_ONE_MINUS_SRC_ALPHA)
and with a glColor4f(1,1,1,1) i get nice white text with a transparant background.
However, I want black text and as I reduce the glColor4f RGB values the text trends towards transparant rather than Black.
I'm guess its using black as its transparant color so i would not be able to get to black text.
My own black textures are working fine however.
Any advice appreciated.

As it says in the Texture2D header, you need to use glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) for text.

I tried using that blend function based on your example in an earlier thread.
However, when using (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) i get a fix black background to the text box rather than transparancy.

Could be a bunch of different things. Did you check out this FAQ, in particular the section on how to debug?

Without seeing more of your code it is a little difficult to come up with many suggestions. You're saying that my example is giving a black background too?

[edit] my other crazy ideas removed because of silliness

Hang on, I think I might know what's up, I'll be back in a few...

Aiight, I think I got it. I'm using the Texture2D from **CrashLanding**, which uses alpha textures for font textures. In the initWithString method in Texture2D.m, make sure it says this for the initWithData call:


Specifically, make sure it is using kTexture2DPixelFormat_A8 for the pixelFormat.

Holy cow, your a genius...I was using the Texture2D from TouchFighter which used a kTexture2DPixelFormat_L8

Changed it to A8 and all is good.

A thousand thanks!

Definitely not genius, just luck and reasoning.

You said you got a black background with my example in that other thread, and I know that should not have happened. So I reasoned it must have been either: 1) somehow rendered wrong before it was handed over to the GL -- OR-- 2) somehow handed over to the GL with the wrong settings

So I ran with number 2, did some testing, and here we are!

Glad you got it working