Patent ID: 8384959
Filing Date: 2013-02-26
Classification: H04N

Abstract:
1. A threshold matrix generating method in a computer comprising a processor and a memory, for generating a threshold matrix which is compared with a grayscale original image in halftoning said original image, comprising the steps of: a) assigning a plurality of stripe pattern areas, which are set in a matrix area in said memory and cross one another, to one of two element groups which correspond to two grayscale ranges and assigning remaining areas to the other of said two element groups, said matrix area being an area where a threshold matrix is generated in said memory, and a plurality of elements are arranged in a row direction and a column direction, said plurality of stripe pattern areas being tilted relatively to said row direction and said column direction, said two grayscale ranges being acquired by dividing a whole grayscale range; b) specifying arbitrary one element in each element group to change said one element to a specified element and subsequently repeating a process of changing another element in said each element group to a specified element, said another element being farthest from specified elements in said each element group, on the premise of spatial repetition of said threshold matrix in halftoning of an original image, or repeating said process in accordance with a predetermined condition, to determine a turn-on order in which halftone dots are added to elements in said each element group in accordance with increase in gray level in a grayscale range corresponding to said each element group or a turn-off order in which halftone dots are removed from elements in said each element group in accordance with decrease in gray level in said grayscale range; and c) determining a threshold value of each element in said matrix area in accordance with a turn-on order(s) and/or a turn-off order(s) for said two element groups.