Fast fourier color constancy

A method comprising:

• obtaining, by a computing device, an input image, wherein the input image comprises a plurality of pixels having respective colors;
• based on the colors of the pixels of the input image, generating a toroidal chrominance histogram, wherein each element of the toroidal chrominance histogram corresponds to a number of pixels of the input image having chrominance values at a respective set of locations within a chrominance space, wherein the set of locations within the chrominance space for a particular element of the toroidal chrominance histogram are regularly spaced within the chrominance space;
• convolving the toroidal chrominance histogram with a filter to generate a two-dimensional heat map;
• determining an illumination chrominance for the input image, wherein the illumination chrominance is determined based on the two-dimensional heat map;
• and
• based on the determined illumination chrominance, tinting the input image to generate a color-corrected output image.

An image capture device comprising:

• an image sensor;
• at least one processor;
• memory;
• and
• program instructions, stored in the memory, that upon execution by the at least one processor cause the image capture device to perform operations comprising:
• operating the image sensor to obtain an input image;
• based on colors of the input image, generating a toroidal chrominance histogram of the input image, wherein each element of the toroidal chrominance histogram corresponds to a number of pixels of the input image having chrominance values at a respective set of locations within a chrominance space;
• convolving the toroidal chrominance histogram with a. filter, wherein the convolution defines a two-dimensional map;
• selecting an entry in the two-dimensional map that represents a particular value that is within a threshold of a maximum value in the map;
• and
• based on the selected entry, tinting the input image to form an output image.