Apparatus, method, and program product for color correction

• US 20070195346A1
• Filed: 02/20/2007
• Published: 08/23/2007
• Est. Priority Date: 02/23/2006
• Status: Abandoned Application

• Current Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Original Assignee: NEC Electronics Corporation (Renesas Electronics Corporation)
• Inventors: Fuji, Kazuhiro
• Application Number:
  US11/708,052
• Publication Number:
  US 20070195346A1
• Time in Patent Office: Days
• US Class Current: 358/1.9
• CPC Class Codes: H04N 1/58 Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction H04N1/62 takes precedence
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence

Abstract

A color correction apparatus of this invention includes a correction unit to correct a color of an input pixel having a color included in a particular region of a color space, and a correction amount calculator to change an amount of the color correction in a nonlinear manner in an order of colors disposed from inside the particular region to a boundary. The correction amount calculator gradually decreases the color correction amount from inside the particular region to the boundary, so that the correction amount decreases to 0 at the boundary.

Claims

1. A color correction apparatus comprising:

a correction unit to correct a color of an input pixel having a color included in a particular region of a color space; and

a correction amount calculator to change an amount of the color correction in a nonlinear manner in an order of colors disposed from inside the particular region to a boundary.

2. The color correction apparatus according to claim 1, wherein the correction amount calculator gradually decreases the color correction amount from inside the particular region to the boundary, so that the correction amount decreases to 0 at the boundary.

3. The color correction apparatus according to claim 2, wherein the correction amount calculator comprises a decrease trend controller that controls the decrease trend of the color correction amount at least once.

4. The color correction apparatus according to claim 3, wherein the decrease trend controller controls an approximation indicating an approximation of the input pixel to a target color to be corrected to be in the decrease trend, and the correction amount calculator further comprises a correction amount processing unit that calculates the color correction amount according to the approximation.

5. The color correction apparatus according to claim 4, wherein the decrease trend controller controls the approximation to be in the decrease trend by a broken line function having at least two decrease trends.

6. The color correction apparatus according to claim 5, wherein the decrease trend controller selects either a first approximation obtained by a first linear function or a second approximation obtained by a second linear function.

7. The color correction apparatus according to claim 6, wherein the decrease trend controller selects a maximum value from the first and the second approximation calculated by Formula 1 and Formula 2 below,

hx_—

a=1−

mul*D 

 

Formula 1 (if hx_a<

0 then hx_a=0)

hx_—

b=limit−

mul2*D 

 

Formula 2 (if hx_b<

0 then hx_b=0)

wherein the mul and the mul2 are weight coefficients specifying the decrease trend, the limit is an approximation limit, the D is a distance between the input pixel and the target color in the color space, hx_a is the first approximation, and hx_b is the second approximation.

8. The color correction apparatus according to claim 4, wherein the decrease trend controller continuously suppresses the decrease trend of the approximation.

9. The color correction apparatus according to claim 8, wherein the decrease trend controller controls the approximation to be in the decrease trend by a multidimensional function.

10. The color correction apparatus according to claim 9, wherein the decrease trend controller calculates the approximation by Formula 3 below,

hx=((Range−

|D|)²)/(Range²) 

 

Formula 3 (if |D|>

Range then hx=0)

wherein the Range is a range of the particular region, the D is a distance between the input pixel and the target color in the color space, and the hx is the approximation.

11. The color correction apparatus according to claim 9, wherein the decrease trend controller calculates the approximation by Formula 4 below,

hx=(2*(Range−

|D|)³)/(Range³)−

(3*(Range−

|D|)²/(Range²)+1 

 

Formula 4 (if |D|>

Range then hx=0)

wherein the Range is a range of the particular region, the D is a distance between the input pixel and the target color in the color space, and the hx is the approximation.

12. The color correction apparatus according to claim 8, wherein the decrease trend controller selects either a first approximation obtained by a first multidimensional function or a second approximation obtained by a second multidimensional function.

13. The color correction apparatus according to claim 12, wherein the decrease trend controller selects the first approximation calculated by Formula 5 below if |D|<

=Pos, selects the second approximation calculated by Formula 6 below if |D|<

=Range, and sets to 0 if |D|>

Range,

hx_—

p=−

(|D|²)/(Range*Pos)+1 

 

Formula 5

hx_—

r=((Range−

|D|)²)/(Range*(Range−

Pos)) 

 

Formula 6

wherein 0<

=Pos<

=Range, and

the Range and the Pos are ranges of the particular region, the D is a distance between the input pixel and the target color in the color space, the hx_p is the first approximation, and the hx_r is the second approximation.

14. A method for color correction to correct a color of an input pixel having a color included in a particular region of a color space, the method comprises:

changing an amount of the color correction in a nonlinear manner in an order of colors disposed from inside the particular region to the boundary.

15. The method according to claim 14, wherein the color correction amount is gradually decreased from inside the particular region to the boundary, so that the correction amount decreases to 0 at the boundary.

16. The color correction method according to claim 15, wherein the decrease trend of the color correction amount is controlled for at least once.

17. A program product for executing a color correction process by a computer to correct a color of an input pixel having a color included in a particular region of a color space, the program product comprises:

changing an amount of the color correction in a nonlinear manner in an order of colors disposed from inside the particular region to the boundary.

18. The program product according to claim 17, wherein the color correction amount is gradually decreased from inside the particular region to the boundary, so that the correction amount decreases to 0 at the boundary.

19. The program product according to claim 18, wherein the decrease trend of the color correction amount is controlled for at least once.