1. A method performed by a software process executing on a computer system, the method comprising: obtaining a digital image comprising a plurality of pixels encoded in a YUV color space, each pixel having a luma component of value Y, a blue color-difference component of value U and a red color-difference component of value V; for a specified pixel having a point (U,V) in a U-V color plane, calculating whether U is less than a first threshold and V is greater than a second threshold, and a chroma value as a distance of the point (U, V) from an origin on the U-V color plane, wherein the distance of the point (U, V) from the origin on the U-V color plane is calculated as an average of U and V; and determining, based on a result of the calculation, whether the specified pixel potentially depicts an orange hue, and if so, whether the specified pixel potentially depicts human skin.