1. A method for gamut size estimation in image processing, comprising: obtaining a color image; processing, by a computer processor, each of a plurality of pixels of the color image by— determining a gamut boundary value for a pixel, wherein the gamut boundary value identifies a smallest size gamut that encapsulates the pixel, and updating a bin of a gamut boundary histogram that corresponds to the gamut boundary value; and determining, by the computer processor, a gamut size metric based on the gamut boundary histogram, wherein the gamut size metric is indicative of a minimum gamut needed to represent the color image.