I try to get the color #ff00ff transparent without much luck.

This makes the entire sprite transparent and thats really not what I want to do.

This is how it looks right now


This is how I want it to look


Best regards!

Unrelated to your problem but you should probably be using GL_QUAD instead of GL_POLYGON (since it seems you're just drawing a quad).

I'm a little tired right now, but basically what it looks like you're doing is drawing a rectangle and putting a texture on it. Your texture is an RGB image with a purple background that you want to represent transparency.

Pretty sure that call to glColor* is setting the color to white with an alpha/opacity value of 0.8 [which is probably not what you intend].

Basically what you need to do is to put your image into a format that stores alpha [ie. opacity] values, f.ex. TGA. OpenGL doesn't know that #ff00ff means transparent, because #ff00ff is just another RGB color. Transparency in OpenGL is handled by playing with the alpha value [ie. RGBA = Red Green Blue Alpha].

You could try to do some kind of color masking to convert your RGB texture to a RGBA texture during runtime, but I think that would be a lot more work.

I wrote a TGA loader snippet I believe that supported loading uncompressed 24bit TGAs if you want to take a look.

Hope all of that makes sense, I need sleep.