Image processor and color image processor

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 plurality of dither threshold planes on which thresholds in a predetermined threshold range corresponding to a tone range of said input image data are arranged on said plurality of dither threshold planes, and for providing halftone-processed image data, each of the plurality of dither threshold planes including a plurality of same unit threshold matrixes;
• 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
• each of said unit threshold matrixes includes a plurality of sub-matrixes on not less than one dither threshold plane;
• an array of relatively low thresholds in said predetermined threshold range is equal among said plurality of sub-matrixes;
• and relatively medium and high thresholds in said predetermined threshold range are arranged aperiodically to extend over series of sub-matrixes.

An image processor for converting input image data having M tones per pixel into image data having N tones for K pixels by a halftone processing, and for outputting an image corresponding to the image data, K set not more than 2 and N set not more than 2, said image processor comprising:

• image conversion means for converting said input image data by the halftone processing using a reference threshold array, and for providing the 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 image conversion means, wherein
• said reference threshold array includes a plurality of unit threshold matrixes of same size;
• an array of relatively low thresholds in a threshold range of the reference thresholds for determining thresholds of the unit threshold matrix is a periodic array in the unit threshold matrix;
• and an array of relatively medium thresholds and high thresholds is an aperiodic array in the unit threshold matrix.

An image processor for converting color input image data having a first number of tones into color image data having a second number of tones lower than said first number by a halftone processing, and for outputting a color image corresponding to the image data, said image processor comprising:

• halftone processing means for carrying out the halftone processing using a dither threshold plane for each color, and for providing said halftone-processed image data, said dither threshold plane including a plurality of unit threshold matrixes of same size;
• and
• image output means having intrinsic, basic tone characteristics, for outputting a color image corresponding to said halftone-processed image data provided from said halftone processing means, wherein
• for at least two color components, each of said unit threshold matrixes includes a plurality of sub-matrixes, an array of relatively low thresholds in a threshold range of reference thresholds for determining thresholds of the unit matrix is equal among said plurality of sub-matrixes, and relatively medium and high thresholds in said predetermined threshold range are arranged aperiodically to extend over series of sub-matrixes.

An image processor for converting color 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 halftone-processing the input image data using a dither threshold plane, and for providing the 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 the plurality of unit threshold matrixes includes a plurality of sub-matrixes;
• a relatively low threshold array in a threshold range of reference thresholds for determining the unit threshold matrix is equal among said plurality of sub-matrixes and an array of relatively medium to high thresholds in said threshold range is an aperiodic array over said plurality of sub-matrixes for at least two types of color components;
• and a threshold array for color components other than said two color components is a periodic and ordered array in said unit threshold matrix in an entire threshold range.

An image processor for converting color input image data having a first number of tones into image data of 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 halftone-processing the input image data using a dither threshold plane, and for providing the 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 the plurality of unit threshold matrixes includes a plurality of sub-matrixes;
• a relatively low threshold array in a threshold range of reference thresholds for determining the unit threshold matrix is equal among said plurality of sub-matrixes and an array of relatively medium to high thresholds in said threshold range is an aperiodic array over said plurality of sub-matrixes for at least two types of color components, wherein
• said halftone processing means carries out the halftone processing using said threshold array for said at least two types of color components, and carries out the halftone processing based on an error diffusion processing for color components other than said two color components.