In one embodiment, pixels that cannot change their color due to the alpha blend mode and the color already stored in a render target are detected. For example, if destination alpha blending is used and a target pixel has an alpha value of 1.0, it will not change color regardless of the computed color of subsequently composited objects. Both computing the object colors and accessing the frame buffer can be avoided when such a case is detected. This may save computations and bandwidth in some embodiments.