use cv2 function

added color_histogram.py sample
work on VideoSynth (chessboard)

samples/python2/color_histogram.py

@@ -0,0 +1,51 @@
+import numpy as np
+import cv2, cv
+from time import clock
+import sys
+
+import video
+
+hsv_map = np.zeros((180, 256, 3), np.uint8)
+h, s = np.indices(hsv_map.shape[:2])
+hsv_map[:,:,0] = h
+hsv_map[:,:,1] = s
+hsv_map[:,:,2] = 255
+hsv_map = cv2.cvtColor(hsv_map, cv.CV_HSV2BGR)
+cv2.imshow('hsv_map', hsv_map)
+
+cv2.namedWindow('hist', 0)
+hist_scale = 10
+def set_scale(val):
+    global hist_scale
+    hist_scale = val
+cv.CreateTrackbar('scale', 'hist', hist_scale, 32, set_scale)
+
+try: fn = sys.argv[1]
+except: fn = 'synth:bg=../cpp/baboon.jpg:class=chess:noise=0.05'
+cam = video.create_capture(fn)
+
+t = clock()
+while True:
+    flag, frame = cam.read()
+    cv2.imshow('camera', frame)
+    
+    small = cv2.pyrDown(frame)
+
+    hsv = cv2.cvtColor(small, cv.CV_BGR2HSV)
+    dark = hsv[...,2] < 32
+    hsv[dark] = 0
+    h = cv2.calcHist( [hsv], [0, 1], None, [180, 256], [0, 180, 0, 256] )
+
+
+    h = np.clip(h*0.005*hist_scale, 0, 1)
+    vis = hsv_map*h[:,:,np.newaxis] / 255.0
+    cv2.imshow('hist', vis)
+    
+
+    t1 = clock()
+    #print (t1-t)*1000
+    t = t1
+
+    ch = cv2.waitKey(1)
+    if ch == 27:
+        break