1. A digital image processing system comprising: an index mapping module to determine a rotation angle index to control the rotation of an input patch of an image based on the (x,y) pixel coordinates of the image patch; a rotation module to rotate the input patch of the image based on the rotation angle index; and a filter engine module applied to a rotated version of the input patch of the image wherein the filter engine module applies a set of fixed filters whose outputs are combined as a weighted sum, and wherein the combination is based on linear weighting coefficients that are computed based on a radius of the input patch.