Grid adaptive interpolation filters

A general framework for image interpolation in a uniformly spaced image grid is presented. The proposed formulation is suitable for representing fractional (or sub-pixel) pixels as well as integer pixel interpolations. Also, by fitting an interpolation kernel to the grid formulation, finite impulse response filter coefficients can be readily determined for a given sampling interval and filter length. As an example, a four-tap lowpass filter is derived by fitting the Lagrange interpolation kernel to a row (or column) expansion by 2 on integer pixel locations.