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.'
        

Hi! I liked this very much. While I understand most images are RGB, some are not. I wanted to write it in a way that could work with any image color mode: https://gist.github.com/dyspop/77b220a38e4309326bdf802ac9ac1b64

The above returns { 'R': 100, 'G': 101, 'B': 12 }

I'd like it to really return { 'RGB' : (100, 101, 12) } but I couldn't figure out how to do that and support producing tuples of unknown length

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]