ADJUSTING AN IMAGE ACCORDING TO AMBIENT LIGHT CONDITIONS

• US 20170324940A1
• Filed: 05/05/2016
• Published: 11/09/2017
• Est. Priority Date: 05/05/2016
• Status: Active Grant

• Current Assignee: NVIDIA Corporation
• Original Assignee: NVIDIA Corporation
• Inventors: DUTTA, Santanu
• Granted Patent: US 10,200,571 B2
• Time in Patent Office: Days
• CPC Class Codes: H04N 1/6086 by scene illuminant, i.e. conditions at the time of picture capture, e.g. flash, optical filter used, evening, cloud, daylight, artificial lighting, white point measurement, colour temperature
• CPC Class Codes: H04N 1/6088 by viewing conditions, i.e. conditions at picture output
• CPC Class Codes: H04N 9/73 Colour balance circuits, e.g. white balance circuits or colour temperature control camera processing pipelines for colour balance H04N23/88

Abstract

An image of an object under a first illuminant is captured. The color of the ambient light at a device on which the image is to be displayed is identified. The image data is adjusted to compensate for the color of the ambient light as well as for the color of the first illuminant. An image based on the adjusted image data can then be displayed on the device. As such, the desired perception of the colors in the displayed image can be managed so that image quality is maintained even if the image is displayed under different ambient lighting conditions.

Claims

1. A method of image processing, the method comprising:

identifying a color of a second illuminant at a device;

accessing first image data for a first image of an object, the first image data captured with the object under a first illuminant;

generating adjusted image data from the first image data by applying factors to the first image data, wherein the factors are derived using both a color of the first illuminant and the color of the second illuminant, and wherein the adjusted image data compensates for the color of the second illuminant; and

displaying on the device a second image rendered from second image data that is based on the adjusted image data.

2. The method of claim 1, wherein said identifying the color of the second illuminant comprises sensing, with a sensor coupled to the device, the color of ambient light at the device.

3. The method of claim 2, wherein said generating is performed automatically in response to said sensing.

4. The method of claim 1, wherein said identifying the color of the second illuminant comprises receiving a user input that selects the color of the second illuminant.

5. The method of claim 1, further comprising sensing a brightness of ambient light at the device, wherein the brightness of the ambient light is compensated for in the second image data.

6. The method of claim 1, wherein said generating and said displaying comprise:

accessing a device-independent version of image data generated from the first image data;

adjusting the device-independent version of the image data to compensate for the color of the first illuminant and the color of the second illuminant, to produce the adjusted image data;

converting the adjusted image data into device-dependent image data; and

gamma-encoding the device-dependent image data, to generate the second image data.

7. The method of claim 6, wherein the first image data comprises gamma domain non-linear image data, and further comprising generating the device-independent version of the image data by:

inverse-gamma-encoding the first image data to produce inverse-gamma-domain linear image data; and

converting the inverse-gamma-domain linear image data into the device-independent version of the image data.

8. A device, comprising:

a processor;

a display screen coupled to the processor; and

memory coupled to the processor, the memory having stored therein instructions that, when executed, cause the device to perform a method of processing an image comprising an object, the method comprising;

identifying a color of a second illuminant at the display screen;

accessing first image data for a first image of the object, the first image data captured with the object under a first illuminant different from the second illuminant, wherein the first image data comprises color values for the object;

generating adjusted image data from the first image data applying factors to the first image data, wherein the factors are derived using both a color of the first illuminant and the color of the second illuminant, and wherein the adjusted image data compensates the color values for the object according to both the color of the first illuminant and the color of the second illuminant; and

generating second image data from the adjusted image data, wherein the second image data, when rendered, produces on the display screen a second image comprising the object.

9. The device of claim 8, further comprising a sensor coupled to the processor and operable for sensing the color of the second illuminant at the device.

10. The device of claim 9, wherein the sensor is further operable for sensing a brightness of ambient light at the device, wherein the brightness of the ambient light is compensated for in the second image data.

11. The device of claim 9, wherein the sensor comprises a camera.

12. The device of claim 9, further comprising a second sensor coupled to the processor and operable for sensing a brightness of ambient light at the device, wherein the brightness of the ambient light is compensated for in the second image data.

13. The device of claim 8, further comprising a user interface coupled to the processor and operable for receiving an input that selects the color of the second illuminant.

14. The device of claim 8, wherein the method further comprises:

inverse-gamma-encoding the first image data to produce inverse-gamma-domain linear image data;

converting the inverse-gamma-domain linear image data into device-independent image data. adjusting the device-independent image data to compensate for the color of the first illuminant and the color of the second illuminant, to produce the adjusted image data;

converting the adjusted image data into device-dependent image data; and

gamma-encoding the device-dependent image data, to generate the second image data.

15. A method of image processing, the method comprising:

accessing first image data for an image of an object illuminated by a color of a first illuminant, the first image data comprising color values;

identifying a color of a second illuminant at a display device;

transforming the color values by multiplying the color values by a product of first values, second values, and third values, wherein the first values transform the color values into device-independent color values, the second values are derived using both the color of the first illuminant and the color of the second illuminant and transform the device-independent color values to compensate for both the color of the first illuminant and the color of the second illuminant to produce adjusted color values, and the third values transform the adjusted color values into device-dependent color values;

gamma-encoding the device-dependent color values; and

displaying on the display device an image based on second image data comprising the device-dependent color values.

16. The method of claim 15, wherein the first image data comprises inverse-gamma-domain linear image data, wherein the method further comprises, before said transforming, inverse-gamma-encoding gamma-domain image data to produce the first image data.

17. The method of claim 15, wherein said identifying the color of the second illuminant comprises sensing, with a sensor coupled to the display device, the color of the second illuminant at the display device.

18. The method of claim 17, wherein said transforming is performed automatically in response to said sensing.

19. The method of claim 15, wherein said identifying the color of the second illuminant comprises receiving a user input that selects the color of the second illuminant.

20. The method of claim 15, further comprising:

sensing a brightness of ambient light at the display device; and

adjusting the image displayed on the display device according to the brightness of the ambient light.