Automatic white balance method and apparatus

An apparatus for performing Automatic White Balance (AWB), the apparatus comprising:

• a gray filter configured to receive a captured image and select gray regions from the captured image;
• a grid converter coupled to the gray filter and configured to transform the selected gray regions to a predetermined coordinate grid;
• a distance module coupled to the grid converter and configured to determine distances in the predetermined coordinate grid from one or more locations based in part on the selected gray regions to each of a plurality of reference illuminant points, wherein each of the one or more locations comprises a center of gravity of a subset of the gray regions;
• an illuminant estimator coupled to the distance module and configured to determine an illuminant based in part on the distances;
• and
• a white balance gain module coupled to the illuminant estimator and configured to apply a white balance gain to the captured image;
• the white balance gain based in part on the illuminant.

An apparatus for performing Automatic White Balance (AWB), the apparatus comprising:

• means for receiving a captured image;
• means for filtering the captured image to select gray pixels;
• means for determining a location of each of the gray pixels in a coordinate grid:
• means for determining a center of gravity based on locations of a subset of the gray pixels in the coordinate grid:
• means for determining a distance from the center of gravity to each of the plurality of reference illuminant points:
• means for determining an illuminant based in part on the distances;
• and
• means for applying a white balance gain to the captured image based in part on the illuminant.

A method of performing Automatic White Balance (AWB), the method comprising:

• receiving a captured image;
• filtering the captured image to select gray pixels, wherein the gray pixels are selected based at least on comparing Cr based values to Cb based values;
• determining a distance in a coordinate grid from each of a plurality of reference illuminant points to a location in the coordinate grid determined at least in part on the selected gray pixels;
• determining an illuminant based in part on the distances;
• and
• applying a white balance gain to the captured image based in part on the illurninant.

An apparatus for performing Automatic White Balance (AWB), the apparatus comprising:

• a gray filter configured to receive a captured image and select gray regions from the captured image, wherein the gray regions are selected based at least on comparing Cr based values to Cb based values;
• a grid converter coupled to the gray filter and configured to transform the selected gray regions to a predetermined coordinate grid;
• a distance module coupled to the grid converter and configured to determine distances in the predetermined coordinate grid from one or more locations based in part on the selected gray regions to each of a plurality of reference illuminant points;
• an illuminant estimator coupled to the distance module and configured to determine an illuminant based in part on the distances;
• and
• a white balance gain module coupled to the illuminant estimator and configured to apply a white balance gain to the captured image;
• the white balance gain based in part on the illuminant.

A non-transitory storage medium storing a set of instructions, wherein the set of instructions when executed by one or more processors causes the one or more processors to perform:

• receiving a captured image;
• filtering the captured image to select gray pixels;
• determining a distance in a coordinate grid from each of a plurality of reference illuminant points to a location in the coordinate grid determined at least in part on the selected gray pixels, wherein determining the distance to a first reference illuminant point comprises:
• determining a plurality of distances corresponding to a distance from the first reference illuminant point to each gray pixel;
• and
• summing the plurality of distances;
• determining an illuminant based in part on the distances;
• and
• applying a white balance gain to the captured image based in part on the illuminant.