Image forming apparatus, print data generation method and computer program for forming an image with halftone processing that uses constraint data

• US 8,363,251 B2
• Filed: 04/16/2009
• Issued: 01/29/2013
• Est. Priority Date: 04/25/2008
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Watanabe, Yumi, Yanai, Tomokazu
• Primary Examiner(s): GARCIA, GABRIEL I
• Application Number:
  US12/424,816
• Publication Number:
  US 20090268240A1
• Time in Patent Office: 1,384 Days
• Field of Search: 358/1.14, 358/1.15, 358/1.9, 358/2.1, 358/3.03, 358/3.04, 358/3.05, 358/3.06, 358/3.13, 358/3.16, 358/3.18, 358/3.21, 358/3.22, 358/3.23, 358/3.26, 358/505, 358/534, 358/536, 358/540, 358/465, 358/466, 382/275, 382/112, 382/251, 382/252, 382/260, 382/172, 382/167, 382/165, 382/237, 382/268, 382/270, 382/299
• US Class Current: 358/1.15
• CPC Class Codes: B41J 2/2125 by means of nozzle diameter selection
• CPC Class Codes: H04N 1/4052 by error diffusion, i.e. transferring the binarising error to neighbouring dot decisions

Abstract

An image forming apparatus that converts image data into print data is provided. The apparatus includes a conversion unit configured to generate first and second print data from the image data using an error diffusion method, each piece of second print data corresponding to one of the plurality of passes; and a printing unit configured to print the second print data. The conversion unit converts the image data into the first print data using the error diffusion method, generates constraint specifying the non-print pixels in the first print data as non-print pixels in the second print data, and converts the image data into the plurality of pieces of second print data, each piece of second print data being used in one of the plurality of passes, through an error diffusion method with the constraint. The printing unit prints the second print data in each of the plurality of passes.

Claims

1. An image forming apparatus that generates N pieces of print data representing dot patterns to be printed on the same region of a recording medium to form an image represented by image data, the apparatus comprising:

an obtaining unit configured to obtain constraint data that specifies non-print pixels obtained from a result of halftone processing to the image data;

a division unit configured to divide each pixel value of the image data into N values to generate N pieces of input data;

a generation unit configured to generate the N pieces of print data, wherein the generation unit generates at least one of the N pieces of print data by converting the input data by halftone processing that uses the constraint data; and

an updating unit configured to update the constraint data by adding print pixels of k pieces of print data that have been already generated to the constraint data as non-print pixels when the generation unit generates k+1th piece of print data by the conversion.

2. The apparatus according to claim 1, wherein the generation unit generates the Nth piece of print data based on print pixels of N-1 pieces of print data that have been already generated and the result of the halftone processing to the image data.

3. The apparatus according to claim 1, wherein the generation unit determines an output value of each pixel of print data obtained by the conversion based on the constraint data and a threshold value used in the halftone processing.

4. The apparatus according to claim 1, wherein the generation unit performs the halftone processing using error diffusion method.

5. The apparatus according to claim 1, wherein the constraint data obtained by the obtaining unit is obtained by a result of halftone processing using any of the error diffusion method, the mean minimum error method or the ordered dithering method.

6. A method for generating N pieces of print data representing dot patterns to be printed on the same region of a recording medium to form an image represented by image data, the method comprising the steps of:

obtaining constraint data that specifies non-print pixels obtained from a result of halftone processing to the image data;

dividing each pixel value of the image data into N values to generate N pieces of input data;

generating the N pieces of print data, wherein at least one of the N pieces of print data is generated by converting the input data by halftone processing that uses the constraint data; and

updating the constraint data by adding print pixels of k pieces of print data that have been already generated to the constraint data as non-print pixels when the generation unit generates k+1th piece of print data by the conversion.

7. A computer-readable non-transitory storage medium in which is stored a computer program for causing a computer to execute a method for generating N pieces of print data representing dot patterns to be printed on the same region of a recording medium to form an image represented by image data, the method comprising:

obtaining constraint data that specifies non-print pixels obtained from a result of halftone processing to the image data;

dividing each pixel value of the image data into N values to generate N pieces of input data;

generating the N pieces of print data, wherein at least one of the N pieces of print data is generated by converting the input data by halftone processing that uses the constraint data; and

updating the constraint data by adding print pixels of k pieces of print data that have been already generated to the constraint data as non-print pixels when the generation unit generates k+1th piece of print data by the conversion.