A screen system used in the electro-optical reproduction of half-tone pictures in multicolor prints are generated by an algorithm which simulates a continuous tone image containing a range of gray shades from black to white or a color separation. The 'threshold equation' is the key of the invention as it calculates a threshold gray value that is compared to the desired local image value to determine whether that particular point should be 'on' or 'off'. Which points (spots) are 'on' and which are 'off' is determined by the function that assigns a 'threshold' value (the shade at which a pixel changes from 'off' to 'on') based on a pixels 'x' and 'y' coordinates. The generated screen comprises columns and rows of halftone dot centers in which the columns and rows are not perpendicular to each other and the column to column spacing is not equal to the row to row spacing.
Non-perpendicular, unequal frequency non-conventional screen patterns for electronic halftone generation