1. A semiconductor imaging device, comprising: a substrate formed of a semiconductor material; a sensor array of photosensitive elements on said substrate to convert an image into pixel signals; a reconfigurable arithmetic circuit, formed on said substrate, having a plurality of circuit elements and a plurality of switches to perform first and second arithmetic operations on said pixel signals; and a control circuit coupled to control a first set of said switches in said reconfigurable arithmetic circuit to couple a first set of said circuit elements to form a first circuit to perform said first arithmetic operation, and to control a second set of said switches to couple a second set of circuit elements which includes at least part of said first set of circuit elements to form a second circuit to perform said second arithmetic operation.