Programmable multi-task on-chip processing is proposed for improving the performance of CMOS imagers in terms of sensitivity adaptation and image processing capabilities. The current-mode fully analog on-chip processing only performs computations during the readout and analog-to-digital conversion phases, removing the need for any in-pixel or focal-plane processing circuitry. A VLSI implementation, in AMI 0.5?m CMOS process, results in significant silicon area savings as processing circuitry accounts for less than 20% of the imager prototype core area. Only three externally tunable parameters are required to fully define the processing task to be carried out by the 32?32 CMOS imager prototype, which performs sensitivity adaptation, edge detection or image enhancement on read-out.