Image processing method and apparatus employing gray scale images having fewer bits per pixel and gray scale image restoration using small areas of an image window

摘要

Input image data representing the image of a subject imaged by a video camera 9 is applied from an A/D converter circuit 11 to a dither- image generating circuit 13, in which the image data is binarized in accordance with the error diffusion method, whereby dither image data represented by one bit per pixel is obtained. A plurality of small areas each comprising a plurality of pixels are set within a window caused to scan the dither image, and the dither image data is summed in each and every small area by an image restoration circuit 14, whereby gray-level image data, in which each small area serves as one pixel, is restored. Difference or correlation values between the restored image data and text data set in advance with regard to standard images which are different from one another are calculated, for the window at each and every position, by arithmetic circuits 15a15k. The smallest difference or the largest correlation values and the positions of the windows in which this smallest difference or the largest correlation values are produced are respectively sensed by corresponding peak holding circuits 16a16k.