US 8,149,464 B2 · Clustered dot-screen design method, a device to perform the clustered dot-screen design method based on human vision and printer model characteristics, and an image-forming apparatus to output binary images on a designed screen

Abstract

A clustered-dot screen design method, a device to perform the clustered-dot screen design method based on human vision characteristics and printer model characteristics, and an image-forming apparatus to output binary images using designed screens. The clustered-dot screen design method based on the human vision characteristics and the printer model characteristics includes determining positions of a plurality of clustered-dot centers using a predetermined method, and designing a screen by growing specific sub-dots about the cluster centers using a predetermined algorithm according to position information of the cluster centers, the human vision characteristics, and the printer model characteristics. The clustered-dot design method has a high tolerance for defects of printers, since a dot growth sequence about the cluster centers is designed in an optimized method based on the human vision characteristics and the printer model characteristics to have an optimized image quality in output images of the printers, and the dots are clustered about the cluster centers.

Claims35

Dependent claims

A clustered-dot screen design method based on human vision characteristics and printer model characteristics, the method comprising:

determining positions of a plurality of clustered-dot centers using a predetermined method;
and
designing a screen via a screen design device by growing specific sub-dots about the plurality of cluster centers using a predetermined clustered-dot screen design algorithm to obtain a designed binary pattern having a minimum cost function between an original input image and a binary pattern through repetitive corrections of the binary pattern according to position information of the plurality of cluster centers, the human vision characteristics of the specific sub-dot growth sequence, and the printer model characteristics,
wherein the predetermined algorithm comprises a modified Direct Binary Search (DBS) algorithm that minimizes a cost function φ expressed as:
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where (x0[m], y0[m]) for m=0, . . . , M−1 represent coordinates of the plurality of cluster centers, G0 represents a set of coordinates of black sub-dots grown about the cluster centers, G1 represents a set of coordinates of white sub-dots grown about the cluster centers, g[i,j] represents the binary pattern, and {tilde over (e)}[i,j] represents a visual difference value between an input image and a print out of the input image.

146 more elements

A method of determining a clustered-dot screen to form an original image using a predetermined image forming apparatus model, the method comprising:

determining a plurality of cluster centers for a screen via a screen design device;
selecting a sub-dot growth sequence about the plurality of cluster centers;
measuring a difference between a visual perception of the original image and a print out of the original image that is output according to the selected sub-dot growth sequence;
and
adjusting the selected sub-dot growth sequence one or more times to minimize the difference between the visual perception and the print out to determine an optimal sub-dot growth sequence for the predetermined image forming apparatus model,
wherein selecting the sub-dot growth sequence further comprises:
selecting black sub-dots to be closest to the plurality of cluster centers and selecting white sub-dots to be furthest from the plurality of cluster centers,
wherein the adjusting of the selected sub-dot growth sequence comprises determining the following equation:
arg min(e[*],g[*],x0[*],y0[*]) for all g[*],
where e[*] represents the difference between the visual perception and the print out, g[*] represents the selected sub-dot growth sequence used to print the print out, x0[*] and y0[*] represent x and y components of the plurality of cluster centers, and arg min(*) is a function that returns an input value that makes an output value of a function a minimum.

7 more elements

A method of determining a clustered-dot screen to form an original image using a predetermined image forming apparatus model, the method comprising:

designing a plurality of binary patterns via a screen design device to represent a plurality of different gray level image pixels using a predetermined clustered-dot screen design algorithm to obtain a designed binary pattern having a minimum cost function between an original input image and a binary pattern through repetitive corrections of the binary pattern according to cluster center position information, human vision characteristics of specific sub-dot growth sequence, and the predetermined image forming apparatus model;
and
storing the plurality of binary patterns,
wherein the predetermined clustered-dot screen design algorithm comprises a modified Direct Binary Search (DBS) algorithm that minimizes a cost function φ expressed as:
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where (x0[m], y0[m]) for m=0, . . . , M−1 represent coordinates of the plurality of cluster centers, G0 represents a set of coordinates of black sub-dots grown about the cluster centers, G1 represents a set of coordinates of white sub-dots grown about the cluster centers, g[i,j] represents the binary pattern, and {tilde over (e)}[i,j] represents a visual difference value between an input image and a print out of the input image.

146 more elements

A clustered-dot screen design device based on human vision characteristics and printer model characteristics, comprising:

a cluster center location design unit to determine positions of a plurality of clustered-dot centers using a predetermined method;
and
a screen design unit to design a screen using a modified Direct Binary Search (DBS) clustered-dot screen design algorithm based on an argument of the minimum function that minimizes a cost function output according to position information of the cluster centers, the human vision characteristics of a specific sub-dot growth sequence, and the printer model characteristics,
wherein the DBS algorithm clustered-dot screen design algorithm minimizes a cost function φ expressed as:
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where (x0[m], y0[m]) for m=0, . . . , M−1 represent coordinates of the plurality of cluster centers, G0 represents a set of coordinates of black sub-dots grown about the cluster centers, G1 represents a set of coordinates of white sub-dots grown about the cluster centers, g[i,j] represents the binary pattern, and {tilde over (e)}[i,j] represents a visual difference value between an input image and a print out of the input image.

146 more elements

An image processing device usable with an image forming apparatus to determine a clustered-dot screen to form an original image using a model of the image forming apparatus, the image processing device comprising:

a cluster center unit to determine a plurality of cluster centers for a screen;
and
a screen design unit to select a sub-dot growth sequence about the plurality of cluster centers, to measure a difference between a visual perception of the original image and a print out of the original image that is output according to the selected sub-dot growth sequence, and to adjust the selected sub-dot growth sequence one or more times to minimize the difference between the visual perception and the print out to determine an optimal sub-dot growth sequence for the image forming apparatus model,
wherein the selected sub-dot growth sequence is based on an argument of the minimum function that returns an input that minimizes an output of a cost function,
wherein the screen design unit adjusts the selected sub-dot growth sequence using the following equation:
arg min(e[*],g[*],x0[*],y0[*]) for all g[*],
where e[*] represents the difference between the visual perception and the print out, g[*] represents the selected sub-dot growth sequence used to print the print out, x0[*] and y0[*] represent x and y components of the plurality of cluster centers, and arg min(*) is a function that returns an input value that makes an output value of a function a minimum.

4 more elements

An image forming apparatus to determine a clustered-dot screen to form an original image using model information thereof, the apparatus comprising:

a screen design device to design a plurality of binary patterns to represent a plurality of different gray level image pixels using a predetermined clustered-dot screen design algorithm based to obtain a designed binary pattern having a minimum cost function between an original input image and a binary pattern through repetitive corrections of the binary pattern according to cluster center position information, human vision characteristics of a specific dot growth sequence, and the predetermined image forming apparatus model;
and
a storage unit to store the plurality of binary patterns,
wherein the predetermined clustered-dot screen design algorithm comprises a modified Direct Binary Search (DBS) algorithm that minimizes a cost function φ expressed as:
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where (x0[m], y0[m]) for m=0, . . . , M−1 represent coordinates of the plurality of cluster centers, G0 represents a set of coordinates of black sub-dots grown about the cluster centers, G1 represents a set of coordinates of white sub-dots grown about the cluster centers, g[i,j] represents the binary pattern, and {tilde over (e)}[i,j] represents a visual difference value between an input image and a print out of the input image.

146 more elements

Dependencies are inferred from the claim text.

Clustered dot-screen design method, a device to perform the clustered dot-screen design method based on human vision and printer model characteristics, and an image-forming apparatus to output binary images on a designed screen

Life of this patent

Clustered dot-screen design method, a device to perform the clustered dot-screen design method based on human vision and printer model characteristics, and an image-forming apparatus to output binary images on a designed screen

Life of this patent

Abstract

Claims35