Determining the color match between image data and graphics objects

• US 7,649,649 B2
• Filed: 11/17/2005
• Issued: 01/19/2010
• Est. Priority Date: 11/17/2005
• Status: Expired due to Fees

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Eschbach, Reiner, Fan, Zhigang, Rumph, David E.
• Primary Examiner(s): Poon; King Y
• Assistant Examiner(s): SEGURA, JAVIER A
• Application Number:
  US11/282,850
• Publication Number:
  US 20070109569A1
• Time in Patent Office: 1,524 Days
• Field of Search: 358/1.9, 358/3.15, 358/3.24, 358/3.27, 358/518, 382263-270, 382/167
• US Class Current: 358/1.9
• CPC Class Codes: G06T 7/90 Determination of colour characteristics

Abstract

A system/method of color match assessment for electronic documents includes receiving digital data defining a composite electronic document including a raster image object having an edge and a color graphics object bordering the edge of the raster image object. The pixel color values defining the edge of the raster image object are processed to estimate a local color variance of the pixel color values. The local color variance is used to determine if the edge can be color matched to the bordering color graphics object. If the edge can be color matched, a match color for the edge is derived. The match color is associated with the digital data defining the electronic document so that a downstream object color match system can use the match color as needed, e.g., to adjust the color of the bordering color graphics object to ensure a match with the edge of the raster image object when the electronic document is printed using a xerographic printing process.

Claims

1. A method of color match assessment for electronic documents, said method comprising:

(a) receiving into an image processing unit of a xerographic printing apparatus digital data defining a composite electronic document including both a raster image object having an edge and a color graphics object bordering said edge of said raster image object;

(b) processing pixel color values defining said edge of said raster image object to estimate a local color variance of said pixel color values defining said edge, wherein the edge is defined by multiple rows/columns of said pixel color values, and wherein said step of processing pixel color values defining said edge comprises;

calculating a row/column local color variance for each row/column of said pixel color values defining said edge;

comparing said row/column local color variance for each row/column to said threshold;

including said row/column in a low variance region for said edge if said row/column local color variance is below said threshold;

increasing a color matching score that said edge can be color matched based upon an increasing number of rows/columns included in said low variance region for said edge;

(c) determining said edge can be color matched based upon a magnitude of the color matching score, wherein a higher color matching score indicates a greater likelihood that said edge can be color matched;

(d) if said edge can be color matched, deriving a match color for said edge, and associating said match color with said electronic document for use of said match color by a downstream object color match system of said image processing unit;

(e) using said xerographic printing apparatus to print said composite electronic document on paper using ink or toner, wherein part of said composite electronic document is printed using said match color.

2. The method of color match assessment for electronic documents as set forth in claim 1, wherein:

said raster image object comprises multiple edges and wherein said electronic document comprises multiple color graphics objects respectively bordering said multiple edges; and

,

for each one of said multiple edges, in order to derive a match color to be associated with each one of said multiple edges, respectively, said method comprises;

processing pixel color values defining each edge of said raster image object to estimate a respective local color variance of said pixel color values defining each edge;

for each edge, determining the edge can be color matched only if said local color variance of the edge is below a threshold;

for each edge that can be color matched, deriving a respective match color for the edge.

3. The method of color match assessment for electronic documents as set forth in claim 1, wherein said match color is derived as an average of all pixel color values defining said edge.

4. The method of color match assessment for electronic documents as set forth in claim 1, wherein said match color is derived as a weighted average of all pixel color values defining said edge.

5. The method of color match assessment for electronic documents as set forth in claim 4, wherein pixels color values defining said edge and located farther from a center of said raster image object are weighted more in said weighted average as compared to pixel color values defining said edge and located closer to said center of said raster image object.

6. The method of color match assessment for electronic documents as set forth in claim 1, wherein said local color variance of said pixel color values defining said edge is determined as:

V(y)=Σ

|I(x,y)−

I(y)÷

N

where;

V(y) represents the color variance of the row/column of pixel values;

N represents the number of pixel values in the row/column being processed;

Σ

|I(x,y)−

I(y)| represents the sum of the absolutes, meaning the sum of the absolute values of the difference between I(x,y)−

I(y) where I(x,y) is the pixel color value for a pixel being processed and I(y) is the mean of all color pixel values in the row/column being processed.

7. The method of color match assessment for electronic documents as set forth in claim 1, wherein said threshold is set to an actual variance calculated for a row/column when said actual variance is below said threshold.

8. The method of color match assessment for electronic documents as set forth in claim 1, wherein said threshold varies depending upon a location of each row/column of pixel color values defining said edge, wherein said threshold is lower for rows/columns farther from a center of said raster image object.

9. A method of color match assessment for electronic documents, said method comprising:

(a) receiving into an image processing unit of a xerographic printing apparatus digital data defining a composite electronic document including a raster image object having an edge and a color graphics object bordering said edge of said raster image object;

(b) processing pixel color values defining said edge of said raster image object to estimate a local color variance of said pixel color values defining said edge;

(c) using said local color variance to determine if said edge can be color matched;

(d) if said edge can be color matched, deriving a match color for said edge, and associating said match color with said electronic document for use of said match color by a downstream object color match system of said image processing unit;

(e) using said xerographic printing apparatus to print said composite electronic document on paper using ink or toner, wherein part of said composite electronic document is printed using said match color;

wherein said local color variance of said pixel color values defining said edge is determined as;

V(y)=Σ

|I(x,y)−

I(y)÷

N

where;

V(y) represents the color variance of the row/column of pixel values;

N represents the number of pixel values in the row/column being processed;

Σ

|I(x,y)−

I(y)| represents the sum of the absolutes, meaning the sum of the absolute values of the difference between I(x,y)−

I(y) where I(x,y) is the pixel color value for a pixel being processed and I(y) is the mean of all color pixel values in the row/column being processed.