title: How to compare histogram in real time with camera?
body: <p>I try this code for detecting object histogram realtime with the camera and its work :</p>
  
  <pre><code>import cv2
  import numpy as np 
  from matplotlib import pyplot as plt
  
  camera = cv2.VideoCapture(1)
  
  base1 = cv2.imread('base1.png')
  base2 = cv2.imread('base2.png')
  base3 = cv2.imread('base3.png')
  
  #Set hist parameters
  hist_height = 64
  hist_width = 256
  nbins = 32
  bin_width = hist_width/nbins
  hrange = [0,180]
  srange = [0,256]
  ranges = hrange+srange                            # ranges = [0,180,0,256]
  
  #Create an empty image for the histogram
  h = np.zeros((hist_height,hist_width))
  
  while 1:
      grabbed, img = camera.read()
      cam = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
      if not grabbed:
        "Camera could not be started."
        break
  
      histcam = cv2.calcHist([cam], [0], None, [nbins], [0,256])
      cv2.normalize(histcam,histcam, hist_height, cv2.NORM_MINMAX)
      hist=np.int32(np.around(histcam))
  
      for x,y in enumerate(hist):
          cv2.rectangle(h,(x*bin_width,y),(x*bin_width + bin_width-1,hist_height), (255), -1)
  
      #Flip upside down
      h=np.flipud(h)
  
      #Show the histogram
      cv2.imshow('Color Histogram',h)
      h = np.zeros((hist_height,hist_width))
  
      cv2.imshow('img',img)
      k = cv2.waitKey(30) &amp; 0xff
      if k == 27:
          break
  
  camera.release()
  cv2.destroyAllWindows()
  </code></pre>
  
  <p>and I add this code under the code above to compare the histogram :</p>
  
  <pre><code>#Compare the Histogram
  
  base1hsv = cv2.cvtColor(base1,cv2.COLOR_BGR2HSV)
  base2hsv = cv2.cvtColor(base2,cv2.COLOR_BGR2HSV)
  base3hsv = cv2.cvtColor(base3,cv2.COLOR_BGR2HSV)
  
  histbase1 = cv2.calcHist([base1hsv], [0], None, [nbins], [ranges])
  cv2.normalize(histbase1,histbase1,hist_height,cv2.NORM_MINMAX)
  hist=np.int32(np.around(histbase1))
  
  histbase2 = cv2.calcHist([base2hsv], [0], None, [nbins], [ranges])
  cv2.normalize(histbase2,histbase2,hist_height,cv2.NORM_MINMAX)
  
  histbase3 = cv2.calcHist([base3hsv], [0], None, [nbins], [ranges])
  cv2.normalize(histbase3,histbase3,hist_height,cv2.NORM_MINMAX)
  
  for i in xrange(1):
  
      if i == 0 :
          print ("Correlation", cv2.HISTCMP_CORREL)
  
      base1_base1 = cv2.compareHist(histbase1,histbase1, cv2.HISTCMP_CORREL)
      base1_cam = cv2.compareHist(histbase1, histcam, cv2.HISTCMP_CORREL)
      base2_cam = cv2.compareHist(histbase2, histcam, cv2.HISTCMP_CORREL)
      base3_cam = cv2.compareHist(histbase3, histcam, cv2.HISTCMP_CORREL)
      print "Method: {0} -- base1-base1: {1} , base1-cam: {2} , base2-cam: {3} , base3-cam: {4}".format(cv2.HISTCMP_CORREL, base1_base1, base1_cam, base2_cam, base3_cam)
  </code></pre>
  
  <p>the code can run without error
  but print method result not displayed on the terminal? whats wrong with my code?</p>