This paper presents efficient filtering algorithms for the interpolation of sequences using IIR filters. Of the suggested filters, the most efficient in terms of computational complexity consists of a very simple allpass IIR filter in parallel with a pure delay. The nonlinear phase distortions of IIR filters, particularly severe in image processing, are avoided by a zero-phase implementation obtained by a combination of causal and anticausal filters. The proposed approach is more efficient for image zooming applications than other methods and yields visually satisfactory results for most gray-scale images.
Tor A. Ramstad,
Sanjit K. Mitra,
"Efficient image interpolation scheme using hybrid IIR Nyquist filters," Optical Engineering 31(6), (1 June 1992). https://doi.org/10.1117/12.56181