IMAGE INFORMATION SIGNAL PROCESSING APPARATUS FOR IMPROVING REPRODUCED IMAGE QUALITY BY DISCRIMINATING THE TYPE OF INPUT IMAGE AND SELECTING A PARTICULAR PROCESSING IN ACCORDANCE THEREWITH

In an image display system, a picture quality improving circuit is provided for comparing a distribution, in a pixel array of a specified size, of image characteristic signals derived from image information signals each indicating one pixel of the input image with a previously examined distribution of image characteristic signals corresponding to each type of image, to thereby discriminate the type of input image. Further, a binary encoding/dithering selecting circuit responsive to the decision made on the picture type by the image quality improving circuit is provided to binary encode the image information signal applied to the image information output device on the basis of a fixed threshold value, or to dither the image information signal on the basis of variable threshold values, in accordance with the discriminated type of input image. Image information signals corresponding to a character/line image are binary encoded by the fixed threshold value, and the image information signals corresponding to a halftone image or a continuous-tone picture are dithered.