JPS57155542A - Formation of halftone dot for printing - Google Patents

Abstract

PURPOSE:To make various data processings possible and to process the formation of halftone dots quickly by using a computer or the like by digitizing once the densities of an original, then forming halftone dot areas in accordance with a predetermined halftone dot table. CONSTITUTION:A halftone dot of a square centering at the central part between screen lines inclinding roughly at 45 deg. and enclosed by the screen lines is set. The formation of the halftone dots is accomplished by defining the central parts of the screen lines corresponding to the peak positions P1 and P2 of the densities of the original respectively as the centers O1 and O2 of the halftone dots D1 and D2 and the halftone dot areas corresponding to density data are formed in accordance with the predetermined halftone dot table. The halftone dot table is so arranged beforehand by analyzing the density data in a number of stages that the area outputs of the halftone dot table are read roughly concentrically from the central part from the smaller of the values of the density data toward the larger and that they are outputted in order of the peripheral parts and the corner parts during the course of this.