1. Electronic image processing apparatus in which an image signal representing a predetermined array of picture elements, or pels, is applied to a high pass filter acting as an image feature detector whose signal output is added to the output of a low pass filter to provide a feature-enhanced output signal, characterised in that the low pass filter is also arranged to act as an image feature detector and includes a prefilter arranged to filter said image signal and a sampling filter arranged to subsample the prefiltered image signal according to a sparse sampling pattern having non-zero pel weightings regularly spaced at locations that are nonadjacent other non-zero weightings.