How can i avoid mouse clicking on alpha areas in my GUITexture?

I have made a GUITexture and placed it in the middle of my screen. It is a picture of a ring. I want the picture to glow when I click on it BUT i want to avoid the pixels that are transparent (the middle and the four corners of the picture). I have tested the hitTest method and was wondering how i can access a single pixel of the GUITexture.

Ok i figured it out. I seem to have found the relative position of the texture but I was still getting weird results. Did some more research and changed GetPixel() to GetPixelBilinear(). Works wonderfully now! Thanks for the info!