Patent ID: 6714320
Filing Date: 2004-03-30
Classification: H04N

Abstract:
An image processor for converting input image data having a first number of tones into image data having a second number of tones lower than said first number by a halftone processing, and for outputting an image corresponding to the image data, said image processor comprising:halftone processing means for carrying out the halftone processing using a dither threshold plane on which thresholds in a predetermined threshold range corresponding to a tone range of said input image data are arranged on said dither threshold plane, and for providing halftone-processed image data; and image output means having intrinsic, basic tone characteristics, for outputting an image corresponding to said halftone-processed image data provided from said halftone processing means, wherein said dither threshold plane includes a plurality of unit threshold matrixes of same size; each of said unit threshold matrix includes a plurality of sub-matrixes; an array of relatively low thresholds in said predetermined threshold range of a reference threshold for determining thresholds of the unit threshold matrix is equal among the plurality of sub-matrixes; and relatively medium thresholds and high thresholds in said predetermined threshold range are arranged aperiodically to extend over series of sub-matrixes.