Patent ID: 9124842
Filing Date: 2015-09-01
Classification: H04N

Abstract:
1. An image data generation method of generating halftone image data through halftone processing performed on a multi-tone color image that includes images of a plurality of color components, the method comprising: a) performing halftone processing on each image of at least one color component among said plurality of color components to generate single-color halftone image data regarding each of said at least one color component, said single-color halftone image data indicating sizes of a plurality of dots that are respectively to be formed at a plurality of pixel positions that are arranged in a matrix in a halftone image region; b) obtaining a hue of each pixel that corresponds to each pixel position in said color image, and in a case where the hue of said each pixel is within a first hue range, determining that a threshold dot size at said each pixel position for a target color component is a predetermined reference threshold dot size, said target color component being included in said plurality of color components and being one color component other than said at least one color component, and in a case where the hue of said each pixel is within a second hue range in which coloration of said target color component is stronger than in said first hue range, determining that said threshold dot size is a predetermined corrected threshold dot size that is larger than said reference threshold dot size; and c) performing halftone processing on an image of said target color component with reference to the single-color halftone image data regarding said at least one color component to generate single-color halftone image data that indicates sizes of a plurality of dots of said target color component that are respectively to be formed at said plurality of pixel positions in said halftone image region, said operation c) including: c1) performing halftone processing on one pixel in the image of said target color component and provisionally determining a size of a dot of said target color component that is to be formed at a pixel position corresponding to said one pixel; c2) obtaining a total dot size that is a sum of a previous total dot size and a provisional dot size, said previous total dot size being a sum of sizes of dots of said at least one color component that are to be formed at said pixel position, and said provisional dot size being the size of the dot of said target color component that is provisionally determined in said operation c1); c3) comparing said total dot size with a threshold dot size at said pixel position, and in a case where said total dot size is smaller than or equal to said threshold dot size, determining that the size of the dot of said target color component is a size equal to said provisional dot size, and in a case where said total dot size is larger than said threshold dot size, determining that the size of the dot of said target color component is a largest dot size that is within a range of a difference between said threshold dot size and said previous total dot size; c4) in a case where said total dot size is larger than said threshold dot size in said operation c3), changing a pixel value of a group of neighboring pixels at one or more pixel positions that are located around said one pixel and at which the size of the dot of said target color component has not yet been determined, on the basis of a pixel value of said one pixel and a difference between said provisional dot size and the size of the dot of said target color component; and c5) changing said one pixel to a next pixel in accordance with a predetermined processing order of said plurality of pixel positions and repeating said operations c1) to c4).