gistfile1.pyw

import cv
import sys

img = cv.LoadImage(sys.argv[1], 0)
hist = cv.CreateHist([32], cv.CV_HIST_ARRAY, [[0, 255]], 1)
cv.CalcHist([img], hist, 0, None)
hist_img = cv.CreateImage((32*10,255), 8, 3)
(_,max_value,_,_) = cv.GetMinMaxHistValue(hist)

(sizex, sizey) = cv.GetSize(img)

darkcount = 0
for i in range(8):
	darkcount = darkcount + cv.QueryHistValue_1D(hist, i)

if darkcount > (.7 * (sizex * sizey)):
	print "Image is dark."
else:
	print "Image is light."

for h in range(32):
	bin_val = cv.QueryHistValue_1D(hist, h)
	intensity = cv.Round(bin_val * 255 / max_value)
	cv.Rectangle(hist_img, (h*5,255), (h*5+5,255-(intensity*5)), cv.RGB(255,255,255), cv.CV_FILLED)

cv.ShowImage("Histogram", hist_img)
cv.WaitKey(0)