Color printing

• US 20060268295A1
• 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.
• Granted Patent: US 7,508,558 B2
• Time in Patent Office: Days
• US Class Current: 358/1.900
• CPC Class Codes: H04N 1/6022 Generating a fourth subtractive colour signal, e.g. under colour removal, black masking

Abstract

A method of processing cyan, magenta, and yellow color values C1, M1, Y1 including 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 B, Cout, Mout 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; and 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.

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 A2 for Y.

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 A2.

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 A2.

4. The method of claim 1 wherein the first threshold array A1 and the second threshold array A2 are uncorrelated.

5. The method of claim 1 wherein transforming C, M, Y 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.

6. 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.

7. 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 A2 for Y.

8. The method of claim 7 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 A2.

9. The method of claim 7 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 A2.

10. The method of claim 7 wherein the first threshold array A1 and the second threshold array A2 are uncorrelated.

11. The method of claim 7 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.

12. The method of claim 7 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.