Method and system of generating high dynamic range image corresponding to specific scene

• US 8,072,507 B2
• Filed: 01/09/2007
• Issued: 12/06/2011
• Est. Priority Date: 10/20/2006
• Status: Expired due to Fees

• Current Assignee: Primax Electronics Limited
• Original Assignee: Primax Electronics Limited
• Inventors: Fuh, Chiou-Shann, Chen, Kun-Yi, Hsi, Chen-Ning, Chou, Wen-Lung
• Primary Examiner(s): HO, TUAN V
• Application Number:
  US11/621,117
• Publication Number:
  US 20080094486A1
• Time in Patent Office: 1,792 Days
• Field of Search: 348/222.1, 348/229.1, 348/362, 348/365, 348/234
• US Class Current: 348/229.1
• CPC Class Codes: G06T 2207/20208 High dynamic range [HDR] image processing
• CPC Class Codes: G06T 5/92 based on global image properties
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene

Abstract

A method of generating a high dynamic range image corresponding to a specific scene. The method includes shooting a specific scene to generate a base image; selecting a bright area and a dark area from the base image; determining base luminance according to the base image; shooting the specific scene to generate at least a first image, wherein average luminance of a part of the first image corresponding to the bright area of the base image is less than or equal to the base luminance; shooting the specific scene to generate at least a second image, wherein average luminance of a part of the second image corresponding to the dark area of the base image is greater than or equal to the base luminance; and combining at least the first image and the second image into a high dynamic range image corresponding to the specific scene.

Claims

1. A method of generating a high dynamic range (HDR) image corresponding to a specific scene, comprising:

shooting a specific scene to generate a base image;

selecting a bright area and a dark area from the base image;

determining base luminance according to the base image;

shooting the specific scene to generate at least a first image, wherein average luminance of a part of the first image corresponding to the bright area of the base image is less than or equal to the base luminance;

shooting the specific scene to generate at least a second image, wherein average luminance of a part of the second image corresponding to the dark area of the base image is greater than or equal to the base luminance; and

combining at least the first image and the second image into an HDR image corresponding to the specific scene;

wherein the step of selecting the bright area and the dark area from the base image comprises;

dividing the base image into a plurality of blocks;

calculating average luminance of each block individually;

for each base image generated and regardless of the luminance properties of the base image, selecting at least one block whose average luminance lies in a high luminance range as the bright area; and

for each base image generated and regardless of the luminance properties of the base image, selecting at least one block whose average luminance lies in a low luminance range as the dark area.

2. The method of claim 1, wherein the step of determining the base luminance according to the base image comprises:

selecting at least one block whose average luminance lies in a median luminance range as a median area; and

calculating average luminance of the median area to be the base luminance.

3. The method of claim 1, wherein the step of determining the base luminance according to the base image comprises:

calculating average luminance of the bright area and the dark area as a whole to be the base luminance.

4. The method of claim 1, wherein the step of determining the base luminance according to the base image comprises:

utilizing subject luminance of the base image as the base luminance.

5. The method of claim 1, wherein the step of determining the base luminance according to the base image comprises:

utilizing average luminance of the base image as the base luminance.

6. The method of claim 1, wherein the step of shooting the specific scene to generate at least a first image comprises:

decreasing base exposure time utilized for shooting the base image to determine first exposure time;

utilizing the first exposure time to shoot the specific scene to generate a candidate first image;

estimating whether average luminance of a part of the candidate first image corresponding to the bright area of the base image is less than or equal to the base luminance; and

if the estimating result is positive, assigning the candidate first image as the first image.

7. The method of claim 6, wherein the step of shooting the specific scene to generate at least a first image further comprises:

if the estimating result is negative, further decreasing the first exposure time, and executing the step of utilizing the first exposure time and the step of estimating the candidate first image again.

8. The method of claim 1, wherein the step of shooting the specific scene to generate at least a second image comprises:

increasing base exposure time utilized for shooting the base image to determine second exposure time;

utilizing the second exposure time to shoot the specific scene to generate a candidate second image;

estimating whether average luminance of a part of the candidate second image corresponding to the dark area of the base image is greater than or equal to the base luminance; and

if the estimating result is positive, assigning the candidate second image as the second image.

9. The method of claim 8, wherein the step of shooting the specific scene to generate at least a second image further comprises:

if the estimating result is negative, further increasing the second exposure time, and executing the step of utilizing the second exposure time and the step of estimating the candidate second image again.

10. The method of claim 1, wherein the step of combining at least the first image and the second image into the HDR image corresponding to the specific scene comprises:

combining the base image, the first image, and the second image into the HDR image corresponding to the specific scene.

11. The method of claim 1, wherein the step of combining at least the first image and the second image into the HDR image corresponding to the specific scene is performed according to a response function g as follows:

g(Z_ij)=ln E_i+ln Δ

t_j,

wherein Z_ij represents the i^th pixel value in the j^th image, E_i represents scene radiance corresponding to the i^th pixel value, and Δ

t_j represents exposure time corresponding to the j^th image.

12. A system of generating an HDR image corresponding to a specific scene, comprising:

a shooting unit, for shooting a specific scene to generate a base image, at least a first image, and at least a second image;

a deciding unit, coupled to the shooting unit, for selecting a bright area and a dark area from the base image, and determining base luminance according to the base image, wherein for each base image generated and regardless of the luminance properties of the base image the deciding unit divides the base image into a plurality of blocks, calculates average luminance of each block individually, selects at least one block whose average luminance lies in a high luminance range as the bright area, and selects at least one block whose average luminance lies in a low luminance range as the dark area; and

a combining unit, coupled to the shooting unit, for combining at least the first image and the second image into an HDR image corresponding to the specific scene;

wherein average luminance of a part of the first image corresponding to the bright area of the base image is less than or equal to the base luminance, and average luminance of a part of the second image corresponding to the dark area of the base image is greater than or equal to the base luminance.

13. The system of claim 12, wherein the deciding unit further selects at least one block whose average luminance lies in a median luminance range as a median area, and calculates average luminance of the median area to be the base luminance.

14. The system of claim 12, wherein the deciding unit calculates average luminance of the bright area and the dark area as a whole to be the base luminance.

15. The system of claim 12, wherein the deciding unit utilizes subject luminance of the base image as the base luminance.

16. The system of claim 12, wherein the deciding unit utilizes average luminance of the base image as the base luminance.

17. The system of claim 12, further comprising:

a controlling unit, coupled to the shooting unit, for decreasing base exposure time utilized for shooting the base image by the shooting unit to determine first exposure time;

wherein the shooting unit utilizes the first exposure time to shoot the specific scene to generate a candidate first image, the deciding unit estimates whether average luminance of a part of the candidate first image corresponding to the bright area of the base image is less than or equal to the base luminance, and if the estimating result is positive, the deciding unit assigns the candidate first image as the first image.

18. The system of claim 17, wherein if the estimating result is negative, the controlling unit further decreases the first exposure time, the shooting unit utilizes the first exposure time to shoot the specific scene to generate another candidate first image, and the deciding unit estimates whether average luminance of a part of the another candidate first image corresponding to the bright area of the base image is less than or equal to the base luminance.

19. The system of claim 12, further comprising:

a controlling unit, coupled to the shooting unit, for increasing base exposure time utilized for shooting the base image by the shooting unit to determine second exposure time;

wherein the shooting unit utilizes the second exposure time to shoot the specific scene to generate a candidate second image, the deciding unit estimates whether average luminance of a part of the candidate second image corresponding to the dark area of the base image is greater than or equal to the base luminance, and if the estimating result is positive, the deciding unit assigns the candidate second image as the second image.

20. The system of claim 19, wherein if the estimating result is negative, the controlling unit further increases the second exposure time, the shooting unit utilizes the second exposure time to shoot the specific scene to generate another candidate second image, and the deciding unit estimates whether average luminance of a part of the another candidate second image corresponding to the dark area of the base image is greater than or equal to the base luminance.

21. The system of claim 12, wherein the combining unit combines the base image, the first image, and the second image into the HDR image corresponding to the specific scene.

22. The system of claim 12, wherein the combining unit combines at least the first image and the second image into the HDR image corresponding to the specific scene according to a response function g as follows:

g(Z_ij)=ln E_i+ln Δ

t_j,

wherein Z_ij represents the i^th pixel value in the j^th image, E_i represents scene radiance corresponding to the i^th pixel value, and Δ

t_j represents exposure time corresponding to the j^th image.