detect skin tones in an image with libvips and python

skin.py

#!/usr/bin/python

import sys
from vipsCC import *

im = VImage.VImage(sys.argv[1])

try:
    # import to CIELAB with lcms
    # 1 means relative colorimetry
    # this assumes there is a profile there, of course
    cielab = im.icc_import_embedded(1)
except:
    # nope .. use the built-in converter instead
    cielab = im.sRGB2XYZ().XYZ2Lab()

# convert to LCh
lch = cielab.Lab2LCh()

# get the h band
h = lch.extract_band(2)

# find all pixels with a hue in the range 60 - 90 (approximately skin tones)
mask = h.more(60).andimage(h.less(90))

mask.write(sys.argv[2])