Optimized shift-varying filters for image interpolation

Image interpolation involves the operations of zero-padding and lowpass filtering. The lowpass filtering operation can never be implemented exactly due to the finite extent of the imagery and approximate implementation results in truncation error which can be quite objectionable when the original image has very limited extent. We present a methology, useful for interpolating imagery containing lines, edges or other directed features, which implements a shift-varying lowpass filter. This filter is designed to minimize (in a constrained L2sense) the objectionable truncation error. A simple example is presented which illustrates the methodology.