Automatic exposure estimation for HDR images based on image statistics

• US 20100329554A1
• Filed: 06/25/2010
• Published: 12/30/2010
• Est. Priority Date: 06/29/2009
• Status: Active Grant

• Current Assignee: InterDigital Madison Patent Holdings (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Wang, Zhe, Zhai, Jiefu, Llach, Joan
• Granted Patent: US 8,346,009 B2
• Time in Patent Office: Days
• US Class Current: 382/167
• CPC Class Codes: G09G 2340/0428 Gradation resolution change
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82

Abstract

A method for tone mapping high dynamic range images for display on low dynamic range displays wherein high dynamic range images are first accessed. The high dynamic range images are divided the into different regions such that each region is represented by a matrix, where each element of the matrix is a weight or probability of a pixel value. An exposure of each region is determined or calculated by estimating an anchor point in each region such that most pixels in each region are mapped to mid grey and the anchor points are adjusted to a key of the images to preserve overall brightness. The regions are then placed or mapped to zones and exposure values are applied to the regions responsive to the weight or probability. The regions are fused together to obtain a final tone mapped image.

Claims

1. A method for tone mapping high dynamic range images for display on low dynamic range displays comprising the steps of:

accessing high dynamic range images;

dividing the high dynamic range images into different regions such that each region is represented by a matrix, where each element of the matrix is a weight or probability of a pixel value;

determining or calculating exposure of each region by estimating an anchor point in each region;

applying exposure values to the regions responsive to the weight or probability; and

fusing the different regions together to obtain a final tone mapped image.

2. The method of claim 1 wherein most pixels in each region are mapped to mid grey and the anchor points are adjusted to a key of the images to preserve overall brightness.

3. The method of claim 2, further comprising the step of identifying or establishing different perceptual brightness levels for the high dynamic range images.

4. The method of claim 2, further comprising the step of identifying or establishing different perceptual brightness levels for the final tone mapped image.

5. The method of claim 1, further comprising the step of determining regions responsive to luminance data.

6. The method of claim 1, wherein toning mapping is performed based on total luminance.

7. The method of claim 1, wherein tone mapping is performed based on individual colors.

8. A method for tone mapping high dynamic range images for display on low dynamic range displays comprising the steps of:

accessing high dynamic range images;

dividing the high dynamic range images into different regions such that each region is represented by a matrix, where each element of the matrix is a weight or probability of a pixel value;

determining or calculating exposure of each region by estimating an anchor point in each region;

applying exposure values to the regions responsive to the weight or probability;

fusing the different regions together to obtain a final tone mapped image; and

providing a means for user interaction such that mapping between regions and zone is performed responsive to user interaction

9. The method of claim 8 wherein most pixels in each region are mapped to mid grey and the anchor points are adjusted to a key of the images to preserve overall brightness.

10. The method of claim 9, further comprising the step of identifying or establishing different perceptual brightness levels for the high dynamic range images.

11. The method of claim 9, further comprising the step of identifying or establishing different perceptual brightness levels for the final tone mapped image.

12. The method of claim 8, further comprising the step of determining regions responsive to luminance data.

13. The method of claim 8, wherein toning mapping is performed based on total luminance.

14. The method of claim 8, wherein tone mapping is performed based on individual colors.