title: OpenCV detection with different colorspace
body: <p>I am using opencv to detect objects with cascade classifiers trained on grayscale images and then testing detection on different color spaces (images initially color) and calculating precision/recall/harmonic mean.<br>
  im wondering why i get the same results for greyscale and rgb but different in other colorspaces?</p>
  
  <pre><code>      # Read the image
      image = cv2.imread(imagePath)
  
  
      # convert to grayscale (default algorithm)
      if colorspace == "gray":
          colorCVT = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
      elif colorspace == "hsv":
          colorCVT = cv2.cvtColor(image, cv2.COLOR_BGR2HSV)
      elif colorspace == "hls":
          colorCVT = cv2.cvtColor(image, cv2.COLOR_BGR2HLS)
      elif colorspace == "lab":
          colorCVT = cv2.cvtColor(image, cv2.COLOR_BGR2LAB)
      elif colorspace == "luv":
          colorCVT = cv2.cvtColor(image, cv2.COLOR_BGR2LUV)
      elif colorspace == "yuv":
          colorCVT = cv2.cvtColor(image, cv2.COLOR_BGR2YUV)
      elif colorCVT --"rgb"
          colorspace = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
      else:
          colorCVT = image
  
      print('using color mode: '+colorspace)
  
      with open(outputFilename, 'a') as results:
          results.write("Running detection on image:  "+imagePath +"\n")
          results.write("Detecting using trained classifier: "+cascadePath +"\n")
      # results.close()
  
  
      # training PARAMS
      SCALE_FACTOR = 1.02
      MIN_NEIGHBORS = 5
      MIN_SIZE = (10,10)
      MAX_SIZE = (128,128)
  
      # Detect objects in the image
      objects = trainedCascade.detectMultiScale(
          colorCVT,
          scaleFactor=SCALE_FACTOR,
          minNeighbors=MIN_NEIGHBORS,
          minSize=MIN_SIZE,
          maxSize=MAX_SIZE,
          flags = cv2.cv.CV_HAAR_SCALE_IMAGE
      )
  </code></pre>