1. A method performed by a software process executing on a computer system, the method comprising: accessing a digital image in the RGB color space, the digital image comprising a plurality of pixels, each pixel having a red component value, R, a blue component value, B, and a green component value, G; without transforming the digital image to another color space, identifying each pixel in the digital image for which a red component value is greater than or equal to a green component value, R≧G, and for which the green component value is greater than a blue component value, G≧B, for each identified pixel, calculating a chroma value by subtracting the pixel's blue component value from the pixel's red component value, R−B, and determining whether the digital image potentially depicts human skin based at least in part on the calculated chroma value; determining whether the chroma value exceeds a threshold; and performing a face detection by: generating a temporary image by masking a plurality of pixels of the digital image for which the chroma value does not exceed the threshold and performing the face detection on the temporary image; or generating a logical bounding box that encompasses a region of the digital image where the chroma value exceeds the threshold for a plurality of pixels and performing the face detection only on a portion of the digital image within the generated bounding box.