Auto white balance algorithm using RGB product measure
View Patent ↗A method and device is provided for adjusting the white balance of a digital image by adjusting the values assigned to the red, green, and blue subpixels of a pixel in the image. The adjustment to the subpixels is determined by identifying pixels in the image that have an RGB product greater than a threshold value, wherein the threshold value is based at least in part on an average of the RGB products of each pixel in the image and a variance between the RGB products of the pixels and the average of the RGB products.
1. A method comprising:
for a pixel in a digital image, calculating a product of a red component value of the pixel, a green component value of the pixel, and a blue component value of the pixel, wherein the product comprises the pixel's red value (R) multiplied by the pixel's green value (G) multiplied by the pixel's blue value (B);
in response to the product satisfying a condition, determining that the pixel belongs to a particular set of pixels;
determining a gain factor based on red component values of only those pixels that belong the particular set of pixels, green component values of only those pixels that belong to the particular set of pixels, and blue component values of only those pixels that belong to the particular set of pixels;
based at least in part on the gain factor, adjusting at least one of the red component value of the pixel, the green component value of the pixel, and the blue component value of the pixel;
wherein the method is performed by a special purpose computing device.
2. The method of claim 1 wherein:
the condition is that the product is greater than a threshold value; and
the particular set of pixels is a set that includes near-white pixels.
3. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of the method recited in claim 2 .
4. The method of claim 1 , wherein determining the gain factor comprises normalizing an average red component value for the particular set of pixels, an average green component value for the particular set of pixels, and an average blue component value for the particular set of pixels.
5. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of the method recited in claim 4 .
6. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of the method recited in claim 1 .
7. A method comprising:
for a pixel in a digital image, calculating a product of a red component value of the pixel, a green component value of the pixel, and a blue component value of the pixel;
in response to the product satisfying a condition, determining that the pixel belongs to a particular set of pixels;
determining a gain factor based on red component values of only those pixels that belong the particular set of pixels, green component values of only those pixels that belong to the particular set of pixels, and blue component values of only those pixels that belong to the particular set of pixels;
based at least in part on the gain factor, adjusting at least one of the red component value of the pixel, the green component value of the pixel, and the blue component value of the pixel;
wherein the method is performed by a special purpose computing device:
the condition is that the product is at least as high as the product for any other pixel in the image whose subpixels sum to a particular value; and
the particular set of pixels is a set that includes near-gray pixels.
8. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of the method recited in claim 7 .
9. A method comprising:
for a pixel in a digital image, calculating a product of a red component value of the pixel, a green component value of the pixel, and a blue component value of the pixel;
in response to the product satisfying a condition, determining that the pixel belongs to a particular set of pixels;
determining a gain factor based on red component values of only those pixels that belong the particular set of pixels, green component values of only those pixels that belong to the particular set of pixels, and blue component values of only those pixels that belong to the particular set of pixels;
based at least in part on the gain factor, adjusting at least one of the red component value of the pixel, the green component value of the pixel, and the blue component value of the pixel;
wherein the method is performed by a special purpose computing device, and wherein:
the condition is that the product is greater than a threshold value; and
the particular set of pixels is a set that includes near-white pixels, wherein the threshold value is based at least in part on an average RGB product for a plurality of pixels, each pixel in the plurality having an RGB product.
10. The method of claim 9 , wherein the threshold value is based at least in part on a variance value, the variance value determined based at least in part on the average RGB product.
11. The method of claim 10 , wherein the average RGB product is determined based on pixel values in a first frame, and the variance is based on pixel values in a second frame that is different than the first frame.
12. The method of claim 11 , wherein the digital image is a third frame.
13. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of the method recited in claim 12 .
14. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of the method recited in claim 11 .
15. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of the method recited in claim 10 .
16. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of the method recited in claim 9 .
17. A method comprising:
for a pixel in a digital image, calculating a product of a red component value of the pixel, a green component value of the pixel, and a blue component value of the pixel;
in response to the product satisfying a condition, determining that the pixel belongs to a particular set of pixels;
determining a gain factor based on red component values of only those pixels that belong the particular set of pixels, green component values of only those pixels that belong to the particular set of pixels, and blue component values of only those pixels that belong to the particular set of pixels;
based at least in part on the gain factor, adjusting at least one of the red component value of the pixel, the green component value of the pixel, and the blue component value of the pixel;
wherein the method is performed by a special purpose computing device, and wherein:
the condition is that the product is greater than a threshold value; and
the particular set of pixels is a set that includes near-white pixels, wherein the method further comprises:
excluding from the particular set one or more pixels that have a red component value, a green component value, or a blue component value greater than a second threshold value.
18. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of the method recited in claim 17 .
19. A digital image acquisition device comprising:
logic that is operable to:
for a pixel in a digital image, calculate a product of a red component value of the pixel, a green component value of the pixel, and a blue component value of the pixel, wherein the product comprises the pixel's red value (R) multiplied by the pixel's green value (G) multiplied by the pixel's blue value (B);
in response to the product being greater than a threshold value, determine that the pixel belongs to a set of near-white pixels;
determine a gain factor based on red component values of the set, green component values of the set, and blue component values of the set;
based at least in part on the gain factor, adjust at least one of the red component value of the pixel, the green component value of the pixel, and the blue component value of the pixel.
20. The digital image acquisition device of claim 19 , wherein the gain factor is determined based at least in part on normalizing an average red component value for the set of near-white pixels, an average green component value for the set of near-white pixels, and an average blue component value for the set of near-white pixels.
21. A digital image acquisition device comprising:
logic that is operable to:
for a pixel in a digital image, calculate a product of a red component value of the pixel, a green component value of the pixel, and a blue component value of the pixel;
in response to the product being greater than a threshold value, determine that the pixel belongs to a set of near-white pixels;
determine a gain factor based on red component values of the set, green component values of the set, and blue component values of the set;
based at least in part on the gain factor, adjust at least one of the red component value of the pixel, the green component value of the pixel, and the blue component value of the pixel,
wherein the threshold value is based at least in part on an average RGB product for a plurality of pixels, each pixel in the plurality having an RGB product.
22. The digital image acquisition device of claim 21 , wherein the threshold value is based at least in part on a variance value, the variance value determined based at least in part on the average RGB product.
23. A digital image acquisition device comprising:
logic that is operable to:
for a pixel in a digital image, calculate a product of a red component value of the pixel, a green component value of the pixel, and a blue component value of the pixel;
in response to the product being greater than a threshold value, determine that the pixel belongs to a set of near-white pixels;
determine a gain factor based on red component values of the set, green component values of the set, and blue component values of the set;
based at least in part on the gain factor, adjust at least one of the red component value of the pixel, the green component value of the pixel, and the blue component value of the pixel,
wherein the average RGB product is determined based on pixel values in a first frame, and the variance is based on pixel values in a second frame that is different than the first frame.
24. The digital image acquisition device of 23 , wherein the digital image is a third frame.
25. A digital image acquisition device comprising:
logic that is operable to:
for a pixel in a digital image, calculate a product of a red component value of the pixel, a green component value of the pixel, and a blue component value of the pixel;
in response to the product being greater than a threshold value, determine that the pixel belongs to a set of near-white pixels;
determine a gain factor based on red component values of the set, green component values of the set, and blue component values of the set;
based at least in part on the gain factor, adjust at least one of the red component value of the pixel, the green component value of the pixel, and the blue component value of the pixel; and
exclude from the set one or more pixels that have a red component value, green component value, or blue component value greater than a second threshold value.