1. A method performed by a software process executing on a computer system, the method comprising: accessing a digital image comprising a plurality of pixels encoded in a color space that defines hue as a pair of Cartesian coordinates; calculating a chroma value for a specified pixel by determining a distance between a point corresponding to a hue coordinate pair value for the specified pixel in the digital image and a Cartesian origin point; comparing the calculated chroma value to a predetermined threshold; and performing an image processing operation on the digital image based on a result of the comparison, wherein determining the distance between the point corresponding to the hue coordinate pair value and the Cartesian origin point includes averaging the coordinate pair value for the specified pixel.