An input image (IMG1) may be converted to a lower-resolution output image (IMG2) by: determining a location (OP) of an output pixel (P2) with respect to said input image (IMG1), determining values of elements (E) of a filter array (FA1) such that non-zero values of the elements (E) of said filter array (FA1) approximate a paraboloid reference surface (REFS), wherein said reference surface (REFS) has a maximum at a base point (BP), and determining a value of said output pixel (P2) by performing a sum-of-products operation between non-zero values of said elements (E) and values of input pixels (P1) of said input image (IMG1) located at respective positions, wherein said filter array (FA1) is superimposed on said input image (IMG1) such that the location of said base point (BP) corresponds to the location of said output pixel (P2).