1. A method of performing a blur rendering process on an image, comprising: accessing a filtered image and depth map information; determining a plurality of blending coefficients for computing a weighted sum for the image and filtered image, wherein the plurality of blending coefficients define a non-linear transformation comprising a substantially smooth transition from at least one first depth class to at least one second depth class and a substantially sharp transition from the at least one second depth class and the at least one first depth class, wherein the at least one first depth class and the at least one second depth class form at least a portion of a plurality of depth classes; and combining the image and the filtered image into a resulting image using the weighted sum.