IMAGE PROCESSING DEVICE SELECTING HALFTONE METHOD FOR EACH SET OF PIXEL DATA OF IMAGE DATA

• US 20110222124A1
• Filed: 02/15/2011
• Published: 09/15/2011
• Est. Priority Date: 03/15/2010
• Status: Active Grant

• Current Assignee: Brother Kogyo Kabushiki Kaisha (Brother Industries Limited)
• Original Assignee: Brother Kogyo Kabushiki Kaisha (Brother Industries Limited)
• Inventors: KUNO, Masashi
• Granted Patent: US 8,643,904 B2
• Time in Patent Office: Days
• US Class Current: 358/3.03
• CPC Class Codes: H04N 1/405 Halftoning, i.e. converting the picture signal of a continuous-tone original into a corresponding signal showing only two levels
• CPC Class Codes: H04N 1/4052 by error diffusion, i.e. transferring the binarising error to neighbouring dot decisions
• CPC Class Codes: H04N 1/4057 the pattern being a mixture of differently sized sub-patterns, e.g. spots having only a few different diameters multi-toning H04N1/40087

Abstract

An image processing device includes a converting unit, a determining unit, and a halftone unit. The converting unit converts original image data to converted image data by performing a scaling process and a color conversion process on the original image data. The original image data includes a plurality of sets of original pixel data. The converted image data has a plurality of sets of converted pixel data. Each set of converted pixel data corresponds to at least one set of original pixel data. The converting unit produces each set of converted pixel data based on the corresponding at least one set of converted pixel data. Each set of converted pixel data includes a plurality of color values. The plurality of color values corresponds to a plurality of color materials. Each color value indicates an amount of one of the plurality of color materials. The determining unit determines, for each set of converted pixel, whether or not at least one set of original pixel data corresponding to the each set of converted pixel data includes predetermined pixel data. The halftone unit produces output image data based on the converted image data. The halftone unit includes a selecting unit and a pixel data halftone unit. The selecting unit selects, for each set of converted pixel data, a first halftone method when the determining unit determines that all set of at least one set of original pixel data corresponding to the each set of converted pixel data does not include the predetermined pixel data, and a second halftone method different from the first halftone method when the determining unit determines that the at least one set of original pixel data corresponding to the each set of converted pixel data includes the predetermined pixel data. The pixel data halftone unit produces a set of output pixel data for each set of converted pixel data in accordance with one of the first halftone method and the second halftone method selected by the selecting unit.

Claims

1. An image processing device comprising:

a converting unit that is configured to convert original image data to converted image data by performing a scaling process and a color conversion process on the original image data, the original image data including a plurality of sets of original pixel data, the converted image data having a plurality of sets of converted pixel data, each set of converted pixel data corresponding to at least one set of original pixel data, the converting unit producing each set of converted pixel data based on the corresponding at least one set of converted pixel data, each set of converted pixel data including a plurality of color values, the plurality of color values corresponding to a plurality of color materials, each color value indicating an amount of one of the plurality of color materials;

a determining unit that is configured to determine, for each set of converted pixel, whether or not at least one set of original pixel data corresponding to the each set of converted pixel data includes predetermined pixel data; and

a halftone unit that is configured to produce output image data based on the converted image data, the halftone unit including;

a selecting unit that is configured to select, for each set of converted pixel data, a first halftone method when the determining unit determines that all set of at least one set of original pixel data corresponding to the each set of converted pixel data does not include the predetermined pixel data, and a second halftone method different from the first halftone method when the determining unit determines that the at least one set of original pixel data corresponding to the each set of converted pixel data includes the predetermined pixel data; and

a pixel data halftone unit that is configured to produce a set of output pixel data for each set of converted pixel data in accordance with one of the first halftone method and the second halftone method selected by the selecting unit.

2. The image processing device according to claim 1, wherein the output data indicates an output image, the output image including a plurality of pixels, each pixel corresponding to a set of output pixel data, each set of output pixel data indicating whether or not a dot is to be formed in the corresponding pixel, and

wherein the second method is different from the fist method such that dots in a first output image is more irregularly formed than a second output image, the first output image being generated by the first halftone method when the selecting unit selects the first halftone method for all sets of converted pixel data, the second output image being generated by the second halftone method when the selecting unit selects the second halftone method for all sets of converted pixel data.

3. The image processing device according to claim 1, wherein the predetermined pixel data represents black.

4. The image processing device according to claim 1, further comprising a transmitting unit that is configured to transmit the output image data to an image forming unit, the image forming unit forming the output image on a recording medium based on the output image data, the image forming unit reproducing a plurality of colors that is contained in a prescribed color range, the plurality of colors having a plurality of saturations,

wherein the predetermined pixel data represents a color having a saturation largest among the plurality of saturations.

5. The image processing device according to claim 1, wherein the first halftone method is an error diffusion method.

6. The image processing device according to claim 5, wherein each set of converted pixel data represents a converted value;

wherein the pixel data halftone unit includes;

a comparing unit that is configured to determine a set of output pixel data for each set of converted pixel data by comparing a converted value corresponding to the each set of converted pixel data to a threshold value; and

a noise adding unit that is configured to add a noise value to at least one of the converted value and the threshold value when the comparing unit compares the converted value to the threshold value, and

wherein when the selecting unit selects the second halftone method, the noise value generates an irregularity smaller than an irregularity generated by the noise value when the selecting unit selects the first halftone method.

7. The image processing unit according to claim 5, wherein the second halftone method is a dithering method.

8. The image processing unit according to claim 7, wherein the pixel data halftone unit includes:

an error determining unit that is configured to determine an error value by comparing the each output value to the corresponding threshold value when the selecting unit selects the second halftone method; and

an error value storing unit that is configured to store the error value when the selecting unit selects the second halftone method instead of sending the error value to the noise adding unit.

9. The image processing unit according to claim 5, wherein the second halftone method is a fixed threshold method.

10. The image processing unit according to claim 9, wherein the pixel data halftone unit includes:

an error determining unit that is configured to determine an error value by comparing the each output value to the corresponding threshold value when the selecting unit selects the second halftone method; and

an error value storing unit that is configured to store the error value when the selecting unit selects the second halftone method instead of sending the error value to the noise adding unit.

11. The image processing device according to claim 1, wherein each set of original pixel data includes a first color value and a second color value, the first color value corresponding to a first color material, a second color value corresponding to a second color material different from the first color material, the plurality of color materials including the first color material and the second color material;

wherein the determining unit determines, for each set of converted pixel data, whether or not the first color value of at least one set of original pixel data corresponding to the each set of converted pixel data is greater than or equal to a first predetermined pixel value, the first predetermined pixel value corresponding to the first color material,

wherein the determining unit determines, for each set of converted pixel data, whether or not the second color value of at least one set of original pixel data corresponding to the each set of converted pixel data is greater than or equal to a second predetermined pixel value, the second predetermined pixel value corresponding to the second color material,

wherein the selecting unit selects, for each set of converted pixel data, the first halftone method for the first color material when the determining unit determines that all first color value is not greater than or equal to the first predetermined pixel value, and the second halftone method for the first color material when the determining unit determines that at least one first color value is greater than or equal to the first predetermined pixel value,

wherein the selecting unit selects, for each set of converted pixel data, the first halftone method for the second color material when the determining unit determines that all first color value is not larger than or equal to the second predetermined pixel value, and the second halftone method for the second color material when the determining unit determines that at least one first color value is greater than or equal to the second predetermined pixel value, and

wherein the pixel data halftone unit produces a set of output pixel data for each set of converted pixel data by producing a first output pixel value based on the first color value in accordance with one of the first halftone method and the second halftone method selected by the selecting unit and by producing a second output pixel value based on the second color value in accordance with one of the first halftone method and the second halftone method selected by the selecting unit.

12. The image processing device according to claim 1, wherein the original image data indicates an original image having a first size, the original image being divided into a plurality of original grids, each original grid corresponding to a set of original pixel data,

wherein the converted image data indicates a converted image having a second size same as the first size, the converted image being divided into a plurality of converted grids, each converted grid corresponding to a set of converted pixel data,

wherein the converting unit produces the converted image data by reducing the converted image data with a reduction ratio one to a prescribed number, the prescribed number being an integer, the converting unit including:

an acquiring unit that is configured to acquire, for each set of converted pixel data, at least one set of original pixel data satisfying a following condition that each of the at least one set of original pixel data corresponds to the original grid whose part is superposed on the converted grid corresponding to the each set of converted pixel data when the converted image is partially superposed on the original image such that the converted image is shifted, from a position at which the converted image is entirely superposed on the original image, by a prescribed length shorter than a length of one original grid; and

a converted pixel data determining unit that is configured to determine the converted pixel data by calculating a weighted average of the at least one set of original pixel data based on size ratio, each size ratio being defined as a ratio of a size of the part of original grid that is superposed on the converted grid corresponding to the converted pixel data to a size of the converted grid.

13. An image processing method comprising:

converting original image data to converted image data by performing a scaling process and a color conversion process on the original image data, the original image data including a plurality of sets of original pixel data, the converted image data having a plurality of sets of converted pixel data, each set of converted pixel data corresponding to at least one set of original pixel data, the converting unit producing each set of converted pixel data based on the corresponding at least one set of converted pixel data, each set of converted pixel data including a plurality of color values, the plurality of color values corresponding to a plurality of color materials, each color value indicating an amount of one of the plurality of color materials;

determining, for each set of converted pixel, whether or not at least one set of original pixel data corresponding to the each set of converted pixel data includes predetermined pixel data; and

producing output image data based on the converted image data, the producing including;

selecting, for each set of converted pixel data, a first halftone method when all set of at least one set of original pixel data corresponding to the each set of converted pixel data does not include the predetermined pixel data, and a second halftone method different from the first halftone method when the at least one set of original pixel data corresponding to the each set of converted pixel data includes the predetermined pixel data; and

producing a set of output pixel data for each set of converted pixel data in accordance with one of the first halftone method and the second halftone method selected in the selecting step.

14. A non-transitory computer readable storage medium storing a set of program instructions installed on and executed by an image processing device, the program instructions comprising:

converting original image data to converted image data by performing a scaling process and a color conversion process on the original image data, the original image data including a plurality of sets of original pixel data, the converted image data having a plurality of sets of converted pixel data, each set of converted pixel data corresponding to at least one set of original pixel data, the converting unit producing each set of converted pixel data based on the corresponding at least one set of converted pixel data, each set of converted pixel data including a plurality of color values, the plurality of color values corresponding to a plurality of color materials, each color value indicating an amount of one of the plurality of color materials;

determining, for each set of converted pixel, whether or not at least one set of original pixel data corresponding to the each set of converted pixel data includes predetermined pixel data; and

producing output image data based on the converted image data, the producing including;

selecting, for each set of converted pixel data, a first halftone method when all set of at least one set of original pixel data corresponding to the each set of converted pixel data does not include the predetermined pixel data, and a second halftone method different from the first halftone method when the at least one set of original pixel data corresponding to the each set of converted pixel data includes the predetermined pixel data; and

producing a set of output pixel data for each set of converted pixel data in accordance with one of the first halftone method and the second halftone method selected in the selecting step.