def _calc_colour_hist(img):
BINS = <NUM_LIT><EOL>hist = numpy.array([])<EOL>for colour_channel in (<NUM_LIT:0>, <NUM_LIT:1>, <NUM_LIT:2>):<EOL><INDENT>c = img[:, colour_channel]<EOL>hist = numpy.concatenate(<EOL>[hist] + [numpy.histogram(c, BINS, (<NUM_LIT:0.0>, <NUM_LIT>))[<NUM_LIT:0>]])<EOL><DEDENT>hist = hist / len(img)<EOL>return hist<EOL>
calculate colour histogram for each region

the size of output histogram will be BINS * COLOUR_CHANNELS(3)

number of bins is 25 as same as [uijlings_ijcv2013_draft.pdf]

extract HSV