Apparatus and method for enhancing color images

• US 20080144962A1
• Filed: 06/20/2007
• Published: 06/19/2008
• Est. Priority Date: 12/19/2006
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Hyoung-Joon, Baek, Yeul-Min, Kim, Whoi-Yul, Jung, Deuk-Soo, Lee, Jin-Aeon
• Application Number:
  US11/812,582
• Publication Number:
  US 20080144962A1
• Time in Patent Office: Days
• US Class Current: 382/274
• CPC Class Codes: G06T 2207/20016 Hierarchical, coarse-to-fine, multiscale or multiresolution image processing; Pyramid transform
• CPC Class Codes: G06T 5/90 Dynamic range modification of images or parts thereof
• CPC Class Codes: H04N 1/6027 Correction or control of colour gradation or colour contrast H04N1/6058 takes precedence

Abstract

Example embodiments are directed to an apparatus and method for enhancing an image. The method may include extracting contrast data from color image data, generating low resolution image data and band pass image data from the contrast data using a Laplacian pyramid, generating global brightness enhanced image data from the low resolution image data to enhance an overall brightness, generating local contrast ratio enhanced image data from the band pass image data to enhance a local contrast, and/or generating enhanced contrast data from the global brightness enhanced image data and the local contrast ratio enhanced data. The apparatus may include circuitry for performing similar operations.

Claims

1. A method for enhancing image quality of a color image, the method comprising:

extracting contrast data from color image data of the color image;

generating low resolution image data and band pass image data from the contrast data using a Laplacian pyramid;

generating global brightness enhanced image data from the low resolution image data to enhance overall brightness;

generating local contrast ratio enhanced image data from the band pass image data to enhance local contrast; and

generating enhanced contrast data from the global brightness enhanced image data and the local contrast ratio enhanced data.

2. The method of claim 1, further comprising:

outputting enhanced color image data obtained by combining the color image data and the enhanced contrast data.

3. The method of claim 2, wherein the enhanced color image data is proportional to a ratio of the color image data to the contrast data raised to a determining function and proportional to the enhanced contrast data.

4. The method of claim 3, wherein the determining function is obtained by raising the contrast data to a first constant and adding a second constant.

5. The method of claim 4, wherein the first constant and the second constant are between 0 and 1.

6. The method of claim 2, wherein the enhanced color image data is generated using the following Equations:

C_out=(C_in/I_in)^S×

I_out

S=I_in^γ

+β

,

where C_out is the enhanced color image data, C_in is the color image data, I_in is the contrast data, S is a determining function, and γ and

β

are constants between 0 and 1.

7. The method of claim 1, wherein generating global brightness enhanced image data from the low resolution image data comprises:

increasing the brightness of the global brightness enhanced image data in response to a low overall brightness of the low resolution image data; and

decreasing the brightness of the global brightness enhanced image data in response to a high overall brightness of the low resolution image data.

8. The method of claim 7, wherein the global brightness enhanced image data is generated using the following Equation:

LP_TOP′

(x,y)=−

{−

c ln(LP_TOP(x,y))}^a+1,

where LP_TOP′

(x, y) is the global brightness enhanced image data, LP_TOP(x, y) is the low resolution image data, x and y are coordinates of the Laplacian pyramid, and a and c are constants between 0 and 1.

9. The method of claim 1, wherein generating local contrast ratio enhanced image data from the band pass image data comprises:

increasing the contrast of the local contrast ratio enhanced image data in response to a low contrast of the band pass image; and

decreasing the contrast of the local contrast ratio enhanced image data in response to a high contrast of the band pass image data.

10. The method of claim 9, wherein the local contrast ratio enhanced image data is generated using the following Equations:

BP_n′

=G(LP_n+1(x,y))×

BP_n

G(I)=k exp(−

I²/c)+1,

where BP_n′

is the local contrast ratio enhanced image data, I is contrast data, BP_n is the band pass image data, k is a constant greater than 1, LP_n+1(x,y) is low resolution contrast data, and c is a constant between 0 and 1.

11. An apparatus for enhancing image quality of a color image, the apparatus comprising:

a contrast data extracting module configured to extract contrast data from color image data of the color image;

a multi-resolution decomposing module configured to generate low resolution image data and band pass image data from the contrast data using a Laplacian pyramid;

a global brightness enhancing module configured to generate global brightness enhanced image data from the low resolution image data;

a local contrast ratio enhancing module configured to generate local contrast ratio enhanced image data from the band pass image data; and

a combining module configured to combine the global brightness enhanced image data and the local contrast ratio enhanced image data to generate enhanced contrast data.

12. The apparatus of claim 11, further comprising:

a color reproducing module configured to generate enhanced color image data from the enhanced contrast data and the color image data.

13. The apparatus of claim 12, wherein the enhanced color image data is proportional to a ratio of the color image data to the contrast data raised to a determining function and proportional to the enhanced contrast data.

14. The apparatus of claim 13, wherein the determining function is obtained by raising the contrast data to a first constant and adding a second constant.

15. The apparatus of claim 14, wherein the first constant and the second constant are between 0 and 1.

16. The apparatus of claim 12, wherein the color reproducing module is configured to generate the enhanced color image data using the following Equations:

C_out=(C_in/I_in)^S×

I_out

S=I_in^γ

+β

,

where C_out is the enhanced color image data, C_in is the color image data, I_in is the contrast data, S is a determining function, and γ and

β

are constants between 0 and 1.

17. The apparatus of claim 11, wherein the global brightness enhancing module is further configured to increase the brightness of the global brightness enhanced image data in response to a low overall brightness of the low resolution image data and decrease the brightness of the global brightness enhanced image data in response to a high overall brightness of the low resolution image data.

18. The apparatus of claim 17, wherein the global brightness enhancing module is configured to generate the global brightness enhanced image data using the following Equation:

LP_TOP′

(x,y)={−

c ln(LP_TOP(x,y))}^a+1,

where LP_TOP′

(x, y) is the global brightness enhanced image data, LP_TOP(x, y) is the low resolution image data, x and y are coordinates of the Laplacian pyramid, and a and c are constants between 0 and 1.

19. The apparatus of claim 11, wherein the local contrast ratio enhancing module is further configured to increase the contrast of the local contrast ratio enhanced image data in response to a low contrast of the band pass image and decrease the contrast of the local contrast ratio enhanced image data in response to a high contrast of the band pass image.

20. The apparatus of claim 19, wherein the local contrast ratio enhancing module is configured to generate the local contrast ratio enhanced image data using the following Equations:

BP_n′

=G(LP_n+1(x,y))×

BP_n

G(I)=k exp(−

I²/c)+1,

where BP_n′

is the local contrast ratio enhanced image data, I is contrast data, BP_n is the band pass image data, k is a constant greater than 1, LP_n+1(x,y) is low resolution contrast data, and c is a constant between 0 and 1.