Image processor for smoothing and differentiating periodic areas and character areas using coefficients

摘要

An image processor performs emphasis processings suitable for materials to be copied to produce clear copy outputs. The image processor has a digitizing circuit which outputs a digital signal produced by digitizing an image. The processor further has a first detecting circuit which detects an area of the digital signal including a periodic component, a second detecting circuit which detects a character area of the digital signal, and a smoothing circuit which smoothes the digital signal to output a smoothed signal. Either the digital signal or the smoothed signal is selected and outputted by a changeover circuit according to an output of the first detecting circuit. The output of the changeover circuit is differentiated into a plurality of differentiated signals by a differentiating circuit by use of a plurality of different coefficients. One of the differentiated signals is selected and outputted according to the outputs of the first and second detecting circuits.