Reproduction apparatus with selective screening and continuous-tone discrimination

摘要

Automatic identification of continuous-tone segments of an original document so that such segments can be screened is accomplished by converting the original image into a series of electrical signals characteristic of the optical density gray level of image pixels, calculating the gray level histogram for pixels within defined regions of the original image, and providing signals related to the position of the continuous-tone segment on the basis of the gray level histograms for each region of the original image.