Color printing

• US 20060268294A1
• Filed: 05/18/2005
• Published: 11/30/2006
• Est. Priority Date: 05/18/2005
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Yao, Meng, Snyder, Trevor J., Gordon, Michael C., Kroon, Stephen M.
• Granted Patent: US 7,457,015 B2
• Time in Patent Office: Days
• US Class Current: 358/1.900
• CPC Class Codes: H04N 1/52 Circuits or arrangements for halftone screening

Abstract

A method of processing cyan, magenta and yellow color values including half-toning cyan and magenta colors values, and half-toning yellow color values in such a manner that yellow dots tend to be printed next to cyan, magenta or secondary color dots regardless of cyan, magenta, or yellow coverages.

Claims

1. A method of processing cyan, magenta, and yellow color values C1, M1, Y1, comprising:

transforming the C1, M1, Y1 color values to cyan, magenta, and yellow color values C, M, Y in such a manner that each of C, M, Y is not greater than a predetermined maximum value VMAX;

obtaining blue, cyan and magenta output color values by setting B=0, Cout=C, and Mout=M;

if the sum C+M is greater than VMAX, obtaining blue, cyan and magenta output color values B, Cout, Mout such that B+Cout+Mout=VMAX;

half-toning B, Cout, Mout and Y using a first threshold array A1 for B, Cout and Mout, and a second threshold array A1′

for Y, wherein the second threshold array A1′

is replica of the first threshold array A1 that is shifted relative to the first threshold array A1 by one pixel.

2. The method of claim 1 wherein half-toning B, Cout, Mout and Y comprises half-toning B, Cout, Mout and Y using:

If B>

t,  

 

C, M dots are on Else if B+Cout>

t,  

 

 

C dot is on Else if B+Cout+Mout>

t, M dot is on If Y>

t′

, Y dot is on

wherein t is a threshold value of the first threshold array A1 and t′

is a threshold value of the second threshold array A1′

.

3. The method of claim 1 wherein half-toning B, Cout, Mout and Y comprises half-toning B, Cout, Mout and Y using:

If B>

t,  

 

C, M dots are on Else if B+Mout>

t,  

 

 

M dot is on Else if B+ Mout+Cout>

t, C dot is on If Y>

t′

, Y dot is on

wherein t is a threshold value of the first threshold array A1 and t′

is a threshold value of the second threshold array A1′

.

4. The method of claim 1 wherein transforming C1, M1, Y1 comprises:

C=C1
M=M1
Y=Y1
If C>

VMAX, set C=VMAX
If M>

VMAX, set M=VMAX
If Y>

VMAX, set Y=VMAX.

5. The method of claim 1 wherein obtaining blue, cyan and magenta output color values B, Cout, Mout such that B+Cout+Mout=VMAX comprises obtaining blue, cyan and magenta output color values B, Cout, Mout using:

B=C+M−

VMAX
Cout=VMAX−

M
Mout=VMAX−

C.

6. A method of processing by cyan, magenta, yellow and black color values C1, M1, Y1, K1, comprising:

transforming the C1, M1, Y1, K1 color values to cyan, magenta, and yellow color values C, M, Y in such a manner that each of C, M, Y is not greater than a predetermined maximum value VMAX;

obtaining blue, cyan and magenta output color values by setting B=0, Cout=C, and Mout=M;

if the sum C+M is greater than VMAX, obtaining blue, cyan and magenta output color values B, Cout, Mout such that B+Cout+Mout=VMAX;

half-toning B, Cout, Mout and Y using a first threshold array A1 for Cout and Mout, and a second threshold array A1′

for Y, wherein the second threshold array A1′

is replica of the first threshold array A1 that is shifted relative to the first threshold array A1 by one pixel.

7. The method of claim 6 wherein half-toning B, Cout, Mout and Y using a first threshold array A1 for B, Cout and Mout, and a second threshold array A2 for Y comprises half-toning B, Cout, Mout and Y using:

If B>

t,  

 

C, M dots are on Else if B+Cout>

t, C dot is on Else if B+Cout+Mout>

t,  

 

 

M dot is on If Y>

t′

, Y dot is on

wherein t is a threshold value of a first threshold array A1, and t′

is a threshold value of a second threshold array A1′

.

8. The method of claim 6 wherein half-toning B, Cout, Mout and Y using a first threshold array A1 for B, Cout and Mout, and a second threshold array A2 for Y comprises half-toning B, Cout, Mout and Y using:

If B>

t,  

 

C, M dots are on Else if B+Mout>

t, M dot is on Else if B+Mout+Cout>

t,  

 

 

C dot is on If Y>

t′

, Y dot is on

wherein t is a threshold value of a first threshold array A1, and t′

is a threshold value of a second threshold array A1′

.

9. The method of claim 6 wherein transforming C1, M1, Y1, K1 comprises:

C=C1+K1
M=M1+K1
Y=Y1+K1
If C>

VMAX, set C=VMAX
If M>

VMAX, set M=VMAX
If Y>

VMAX, set Y=VMAX.

10. The method of claim 6 wherein obtaining blue, cyan and magenta output color values B, Cout, Mout such that B+Cout+Mout=VMAX comprises obtaining blue, cyan and magenta output color values B, Cout, Mout using:

B=C+M−

VMAX
Cout=VMAX−

M
Mout=VMAX−

C.

11. A method of processing cyan, magenta and yellow color values comprising:

half-toning cyan and magenta colors values;

half-toning yellow color values in such a manner that yellow dots tend to be printed next to cyan, magenta or secondary color dots regardless of cyan, magenta, or yellow coverages.

12. The method of claim 11 wherein:

half-toning cyan and magenta color values comprises half-toning cyan and magenta color values using a threshold array A1;

half-toning yellow color values comprises half-toning yellow color values using a threshold array A1, wherein the threshold array A1′

is a one pixel shifted replica of the threshold array A1.