1. Apparatus for enhancing the image produced from a received video signal, comprising: means sampling the video signal at a predetermined rate to provide a succession of coded samples indicating the instantaneous amplitude of the video signal with each sampling, memory means storing a plurality of said coded samples, means inserting the coded samples into the memory means with each successive sampling of the video signal, means generating an average sample corresponding to the average of a predetermined group of samples stored in the memory means in response to each sampling of the video signal, means generating a median sample corresponding to the median of a predetermined group of samples stored in the memory means in response to each sampling of the video signal, subtraction means for generating a gradient sample with each sampling of the video signal corresponding to the median sample minus the average sample, processing means responsive to the average sample and the gradient sample for generating an output sample proportional to the sum of the average sample and the product of the gradient sample and the absolute value of the gradient sample, and means converting successive output samples to an output video signal.