Method for printing a grayscale raster image by grayscale value dispersion

Patent metadata

Field	Value
Publication number	US-9424499-B2
Application number	US-201514790477-A
Country	US
Kind code	B2
Filing date	Jul 2, 2015
Priority date	Jul 11, 2014
Publication date	Aug 23, 2016
Grant date	Aug 23, 2016

Abstract

A method is provided for enhancing a grayscale raster image comprising pixels. The method comprises the steps of composing a second raster image of equal dimensions to said raster image, selecting a target pixel in the second raster image, having a target position, and deriving a grayscale value for the target pixel from a grayscale value of a pixel in said raster image that is in a neighborhood of a pixel on a position corresponding to the target position, thereby dispersing the gray value of a pixel in a predetermined range around its original position and working the second raster image up for a halftoning process without using pixel segmentation.

First claim

What is claimed is:

1. A method for enhancing a raster image that comprises pixels, a pixel having a position in the raster image and a grayscale value, the method comprising the steps of:
a) defining a second raster image of equal dimensions to said raster image;
b) selecting a target pixel in the second raster image, having a target position;
c) deriving a grayscale value for the target pixel from a grayscale value of a pixel in said raster image that is in a range of a pixel on a position corresponding to the target position, in order to disperse the grayscale value of a pixel in a predetermined range around its original position and to enhance the second raster image for further processing in a halftoning process without using pixel segmentation.

2. The method according to claim 1 , wherein the pixel in said raster image is selected randomly within the range around the target position.

3. The method according to claim 2 , wherein a high-pass filter is applied to enhance a contrast before dispersing a grayvalue.

4. The method according to claim 2 , wherein the range around the target position is dependent on a grayscale value in said raster image.

5. The method according to claim 1 , wherein a high-pass spatial filter in sequence with a low-pass spatial filter is used to disperse a grayscale value with sufficient contrast.

6. The method according to claim 1 , wherein a morphological dilation operation is applied in addition to dispersing a pixel value.

7. The method according to claim 6 , wherein the morphological dilation operation is dependent on the grayvalue of a pixel.

8. Print system comprising a print controller for receiving and converting print jobs into raster images, a print engine for marking image receiving material according to a binary image and an image processing module configured to process a grayscale raster image according to the method according to claim 1 and to process the resulting grayscale raster image into a binary image according to the halftoning process.

Assignees

• Océ-Technologies B V
• Oce Tech Bv

Inventors

• Janssen Johannes H M

Classifications

• G06K15/1881 Primary

  Halftoning (halftoning of still images in general H04N1/405, H04N1/52) · CPC title

• G06K15/1878

  Adjusting colours (image colour correction or control for documents in general H04N1/60) · CPC title

• G06T5/30

  Erosion or dilatation, e.g. thinning · CPC title

• H04N1/409

  Edge or detail enhancement; Noise or error suppression · CPC title

• G06K15/1872

  Image enhancement · CPC title