White balance for video applications

• US 20060262333A1
• Filed: 04/17/2006
• Published: 11/23/2006
• Est. Priority Date: 10/15/2004
• Status: Active Grant

• Current Assignee: Lifesize, Inc. (Enghouse Systems Limited)
• Original Assignee: Lifesize, Inc. (Enghouse Systems Limited)
• Inventors: Jenkins, Michael V.
• Granted Patent: US 7,864,221 B2
• Time in Patent Office: Days
• US Class Current: 358/1.120
• CPC Class Codes: H04L 12/1818 Conference organisation arrangements, e.g. handling schedules, setting up parameters needed by nodes to attend a conference, booking network resources, notifying involved parties
• CPC Class Codes: H04L 43/0811 by checking connectivity
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 7/142 Constructional details of the terminal equipment, e.g. arrangements of the camera and the display
• 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

In some embodiments, images for the video conference may be white balanced. White balancing may include dividing at least a subset of an image'"'"'s pixels into multiple ranges according to their luminance and chrominance values. For example, at least a portion of the pixels in an image may be sorted into different groups (i.e., by incrementing counters respective to each group) according to the luminance and chrominance values of the pixels. If enough pixels are found to be in a particular group, a portion or all of the image may be adjusted by a ratio corresponding to that particular group. For example, blue and red analog gains (corresponding to the selected pixels) may be modified by a corresponding ratio to bring red and blue accumulations closer to green accumulations.

Claims

1. A method for adjusting an image by classifying pixels in the image into different ranges, comprising:

comparing each pixel value of a plurality of pixel values in the image to at least one luminance range;

if the pixel value is in the at least one luminance range, comparing the pixel value to at least one chrominance range;

if the pixel value is in the at least one chrominance range, incrementing a counter; and

if the counter represents a percentage of the plurality of pixel values that is greater than a predetermined percentage, adjusting at least one pixel value by a ratio which results in at least one chrominance value of the adjusted pixel value being closer to a predetermined chrominance value.

2. The method of claim 1, wherein the ratio is calculated using at least two sum values for the plurality of pixel values which are in the plurality of pixel values.

3. The method of claim 2, wherein adjusting at least one pixel value includes adjusting each pixel value in the image by adjusting a camera sensor by the calculated ratio.

4. The method of claim 3, wherein the ratio equals a green sum of the pixel values in the plurality of the pixels divided by a red sum of the pixel values in the plurality of pixels.

5. The method of claim 1, wherein the predetermined percentage is based on a percentage of the number of the plurality of pixel values.

6. The method of claim 1, wherein predetermined percentage is based on a percentage of the total number of pixels in the image.

7. The method of claim 1, wherein the at least one luminance range comprises at least three luminance ranges.

8. The method of claim 1, wherein the at least one chrominance range comprises a blue chrominance range or a red chrominance range.

9. The method of claim 1, wherein the at least one luminance range and the at least one chrominance range are predetermined ranges.

10. The method of claim 1, wherein accumulating a counter includes storing a value of a pixel which resulted in the counter being accumulated.

11. The method of claim 1, wherein the predetermined percentage may vary with time and may be calculated based on an exposure of a previous image in a video stream with the image.

12. A method for adjusting an image by classifying pixels in the image into different ranges, comprising:

comparing each pixel value of a plurality of pixel values in the image to a first luminance range;

if the pixel value is in the first luminance range, comparing the pixel value to a first blue chrominance range;

if the pixel value is in the first blue chrominance range, comparing the pixel value to a first red chrominance range;

if the pixel value is in the first red chrominance range, accumulating a first counter;

if the pixel value is not in the first luminance range, comparing the pixel value to a second luminance range;

if the pixel value is in the second luminance range, comparing the pixel value to a second blue chrominance range;

if the pixel value is in the second blue chrominance range, comparing the pixel value to a second red chrominance range;

if the pixel value is in the second red chrominance range, accumulating a second counter; and

if the first counter represents a percentage that is greater than a first predetermined percentage of the plurality of pixel values, adjusting at least one pixel value by a first ratio which results in at least one chrominance value of the pixels being closer to a predetermined chrominance value.

13. The method of claim 12, wherein the first ratio is calculated using at least two sum values for the plurality of pixel values which are in the plurality of pixel values.

14. The method of claim 13, wherein adjusting at least one pixel value includes adjusting each pixel value in the image by adjusting a camera sensor by the calculated ratio.

15. The method of claim 14, wherein the ratio equals a green sum of the pixel values in the plurality of the pixels divided by a red sum of the pixel values in the plurality of pixels.

16. The method of claim 12, wherein first predetermined percentage is based on a percentage of the total number of pixels in the image.

17. The method of claim 12, further comprising if the first counter does not represent a percentage that is greater than the first predetermined percentage, and the second counter represents a percentage that is greater than a second predetermined percentage, adjusting at least one pixel value by a second ratio which results in at least one chrominance value of the at least one pixel value being closer to a predetermined chrominance value.

18. The method of claim 12, further comprising:

if the pixel value is not in the first or second luminance range, comparing the pixel value to a third luminance range;

if the pixel value is in the third luminance range, comparing the pixel value to a third blue chrominance range;

if the pixel value is in the third blue chrominance range, comparing the pixel value to a third red chrominance range; and

if the pixel value is in the third red chrominance range, accumulating a third counter.

19. The method of claim 18, further comprising if the first counter does not represent a percentage that is greater than the first predetermined percentage, the second counter does not represent a percentage that is greater than the second predetermined percentage, and the third counter represents a percentage that is greater than a third predetermined percentage, adjusting at least one pixel value by a third ratio which results in at least one chrominance value of the pixels being closer to a predetermined chrominance value.