An image sensor and a pre-processing circuit adapted to associate weights respectively with cells of a grid. The cells respectively may include multiple contiguous picture elements of the image sensor. The pre-processing circuit may be configured to adaptively change the weights responsive to changes in the scene being imaged by the image sensor. The number of the cells per distance on the surface of the image sensor may be substantially less than the resolution of the image sensor. The cells which share the same weights may specify a region of interest on the image sensor.