Electronic halftone imaging system

Abstract

An electronic halftoning image reproduction system wherein a halftone screen function is combined with pictorial information, typically by addition, to provide a sum function. In a second channel the pictorial signal is averaged over the area corresponding to one period of the halftone screen function and the average is utilized to determine the percent of the area to be turned white within that halftone dot. This is accomplished by thresholding the sum function with a dynamically adjusted threshold for each period of the halftone dot such that the percentage of white matches the average pictorial signal. In another embodiment wherein the desired gray scale of the reproduction is different from that of the original image, the average pictorial signal may be adjusted in some predetermined manner and the percentage of white is matched to the adjusted signal. In a digital implementation the result is obtained by starting at the sample location with the largest value of the sum function and setting subdots white until the correct area is white. All steps are repeated over each period of the halftone.

Dependencies are inferred from the claim text.