A method for selectively transforming a multi-dimensional input array comprising D dimensions includes, with a computing system, determining a D-dimensional convolution of the input array at only selected points in the array, each the convolution being a function of a product of D one-dimensional kernels; determining partial convolutions at each dimension iteratively, an iterative determination of one of the partial convolutions being determined, in part, from a previous iterative determination; and collecting transformed values from the convolutions into the input array to form a transformed input array.