Method of and apparatus for making a half-tone reproduction of an image

摘要

A method of making a half-tone reproduction of an image includes the step of forming an image consisting of half-tone dots having a greater size at darker image units areas. Each image unit area is divided into a plurality of elements. The elements are formed dark, making up a half-tone dot, or light dependent on the comparison between the reflectivity of a corresponding unit area and values of a half-tone function which is a two-dimensional periodic function of the coordinates of the elements. The method further includes determining variation of the reflectivity of the image in two mutually opposite directions at the place of location of each unit area and comparing the reflectivity with the half-tone function value corresponding to the coordinates of the element shifted with respect to the element to be formed in a direction of a greater decrease in reflectivity, if such a decrease takes place. As a result, the half-tone dots lying on an image contour are shifted towards a darker part of the image. An apparatus for reproduction of an image comprises a light source forming an image and connected to the output of a comparator having its inputs connected to the outputs of a video signal source and of a half-tone function generating unit. The inputs of the latter are connected through adders to the outputs of a unit generating coordinates of the elements of the receiving medium unit areas and to the outputs of coordinate correction units.