1. An image processing system comprising: video signal input means for receiving an original video signal S.sub.org associated with a pixel involved in an original image, the original video signal S.sub.org being formed by scanning the original image; operational circuitry interconnected to said input means for executing an unsharp masking processing in accordance with an expression defined by ##EQU18## to produce a resultant signal S' with respect to a rectangular area formed by N.sub.p scanning lines each including M.sub.p pixels and defined by two lengths of line which are substantially parallel to the direction of a scanning line and two lengths of line which are substantially perpendicular to the direction of a scanning line, wherein .alpha..sub.p is a weight, .beta. is an emphasis function, .gamma. is a nonlinear function, M.sub.p, N.sub.p and P are a natural number, and p is one of P; video signal producing means interconnected to said operational circuitry for producing the resultant signal S' calculated from the expression as a video signal to be reproduced of the original image; wherein said operational circuitry comprises: first and second processors interconnected with each other; said first processor executing operations on the term ##EQU19## in the expression sequentially with respect to the rectangular areas of the original image to transfer the results ##EQU20## together with the associated original video signals S.sub.org to said second processor; said second processor being in response to the results ##EQU21## and the associated original video signals S.sub.org to execute operations on the remaining portions of the expression sequentially with respect to the rectangular areas to form the resultant signal S'.