Image processing apparatus for mixing weighted continuous-tone and unsharp image signals to reduce visible noise in reproduced images

摘要

An image processing apparatus comprises an unsharp signal generating means for processing image signals S obtained from continuous- tone images for average so as to generate unsharp signals U, a weighted parameter generating means for generating weighted parameters P and Q according to the level of the image signals S and the level of the unsharp signals U and an image signal producing means for producing an image signal T according to the following equation:PP T=P·U+Q. multidot.SPPwherePPS is an image signal, U is an unsharp signal andPPP and Q are weighted parameters.PPThe unsharp signal generating means comprises an addition averaging circuit for adding the image signals S corresponding to an even number of pixels arranged to form a continuous- tone image to be scanned in a main scanning direction and for processing the added signals for average, thereby to generate unsharp signals U. The unsharp signal generating means includes a look-up table for establishing the weighted parameters P and Q according to increase in the level of either one of an image signal S and an unsharp signal U and for selecting the weighted parameters P and Q corresponding to the level of the image signal S and unsharp signal U.