JPS57116479A - Image processing circuit - Google Patents

Abstract

PURPOSE:To obtain an image of high quality by preventing the generation of the moire of a mesh-point image and a dithered image by extracting the high-frequency component of an image signal and by inputting only a clock for picture- element transfer to a counter for addressing when the high-frequency component exceeds some threshold value. CONSTITUTION:An image density signal S(i,j) from an image sensor 1 is inputted to a comparator 3 and a filter 10, which extracts a high-frequency component from the image signal. A discriminating circuit 11 compares the value of this extracted high-frequency component with some threshold value and, when the high-frequency component exceeds some threshold value, puts a random access generating circuit 12 in operation to generate random pulses. The random pulses are delayed by a delay circuit 13 and ORed with clock pulses by an OR circuit 14, whose outputs are inputted to a counter 4. Then, the counter 4 reads image information from a dither matrix 5 to a DA converter 6, and the comparator 3 outputs image signals (oi) and (j) to prevent the generation of a moire.