Robust selection and weighting for gray patch automatic white balancing
First Claim
1. A method for calculating a white balance for an image capture device, the method comprising:
- receiving a set of image data comprising a plurality of pixels;
calculating a position in a color space for each of the plurality of pixels, the color space comprising a plot of common lights;
determining a plurality of distances between the positions of the pixels in the color space and the plot of common lights;
sorting the plurality of pixels into a plurality of sample populations based on the distances;
selecting a first sample population from the plurality of sample populations by calculating an estimate of a probability density as a function of distance from the plot of common lights for the plurality of sample populations;
averaging the distances in the first sample population to determine an initial gray point estimate; and
refining the initial gray point estimate into a final gray point estimate.
1 Assignment
0 Petitions
Accused Products
Abstract
Embodiments of the present invention are directed to methods and systems for robust weighting of gray patches in automatic white balancing in an image-capture device by utilizing kernel density estimation techniques with dynamically variable bandwidth to determine the probability density of samples to create an initial estimate, then verifying the initial gray point estimate to account for outliers. In one embodiment, given a set of image data, an initial gray point estimate in a color space is determined for the set of image data. The initial estimate is then refined by weighting the sub-population with the greatest probability of being gray. A final evaluation that includes a further comparison to pre-programmed constraints determines a final estimate, which can still be further tuned according to user preferences by adjusting color biases. The resulting final gray point estimate provides greater stability, and greatly improved accuracy over traditional techniques and solutions.
-
Citations
37 Claims
-
1. A method for calculating a white balance for an image capture device, the method comprising:
-
receiving a set of image data comprising a plurality of pixels; calculating a position in a color space for each of the plurality of pixels, the color space comprising a plot of common lights; determining a plurality of distances between the positions of the pixels in the color space and the plot of common lights; sorting the plurality of pixels into a plurality of sample populations based on the distances; selecting a first sample population from the plurality of sample populations by calculating an estimate of a probability density as a function of distance from the plot of common lights for the plurality of sample populations; averaging the distances in the first sample population to determine an initial gray point estimate; and refining the initial gray point estimate into a final gray point estimate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
-
-
36. A non transitory computer readable medium containing program instructions embodied therein for causing an image capture device to calculate a gray point estimate for a captured image, the program instructions comprising:
-
instructions to receive a set of image data comprising a plurality of pixels; instructions load a set of characterization data corresponding to a color space; instructions to calculate a plot of common lights in the color space and a position in the color space for each of the plurality of pixels; instructions to determine a plurality of distances between the positions of the pixels in the color space and the plot of feasible lights; instructions to sort the plurality of pixels into a plurality of sample populations based on the distances; instructions to select a first sample population from the plurality of sample populations by calculating an estimate of a probability density as a function of distance from the plot of common lights for the plurality of sample populations; instructions to average the first sample population of the plurality of sample populations to determine an initial gray point estimate; and instructions to refine the initial gray point to determine a refined gray point estimate.
-
-
37. A system for calculating a white balance estimate in an image capture device, said system comprising:
-
an image capture device comprising a lens, an image sensor and an image signal processor, the image capture device being configured to generate an image comprising a set of image data; a memory, communicatively coupled to the image capture device, and configured to store the set of image data and a plurality of programmed instructions; and a processor, communicatively coupled to the memory, and configured to execute the plurality of programmed instructions and to calculate a white balance estimate from the set of image data by refining an initial gray point estimate generated from averaging a selection of a plurality of sample pixels comprised in the set of image data and stored in the memory, the selection of the plurality of sample pixels comprising the pixels with corresponding positions in a color space closest to a pre-plotted line based on an application of a probability density function, wherein the initial gray point estimate is refined by applying a kernel density estimator to selection of the plurality of sample pixels to identify a plurality of sub-populations and by taking a weighted average of the plurality of sub-populations, further wherein the white balance estimate is applied to the set of image data.
-
Specification