Average Image Color

average_image_color.py

from PIL import Image

def average_image_color(filename):
	i = Image.open(filename)
	h = i.histogram()

	# split into red, green, blue
	r = h[0:256]
	g = h[256:256*2]
	b = h[256*2: 256*3]

	# perform the weighted average of each channel:
	# the *index* is the channel value, and the *value* is its weight
	return (
		sum( i*w for i, w in enumerate(r) ) / sum(r),
		sum( i*w for i, w in enumerate(g) ) / sum(g),
		sum( i*w for i, w in enumerate(b) ) / sum(b)
	)

if __name__ == '__main__':
    import sys
    if len(sys.argv) > 1:
        print average_image_color(sys.argv[1])
    else:
        print 'usage: average_image_color.py FILENAME'
        print 'prints the average color of the image as (R,G,B) where R,G,B are between 0 and 255.'
        

Are you sure this does what you think it does? I'm thinking it actually takes the full histogram and cuts it up into four parts... I tested this on a single color image and the histograms don't look right to me. I could be wrong.

# split into red, green, blue
	r = h[0:256]
	g = h[256:256*2]
	b = h[256*2: 256*3]