title: OpenCV with Python error - Assertion failed ((mask.type() == CV_8UC1 || mask.type() == CV_8SC1)) in binary_op
body: <p>I am trying to overlay an image over the webcam feed. Here's the main section of the code -</p>
  <pre><code># Load our overlay image: glasses.png
  imgGlasses = cv2.imread('1.png')
       
  # Create the mask for the glasses
  imgGlassesGray = cv2.cvtColor(imgGlasses, cv2.COLOR_BGR2GRAY)
  ret, orig_mask = cv2.threshold(imgGlasses, 10, 255, cv2.THRESH_BINARY)
   
  # Create the inverted mask for the glasses
  orig_mask_inv = cv2.bitwise_not(orig_mask)
   
  # Convert glasses image to BGR
  # and save the original image size (used later when re-sizing the image)
  imgGlasses = imgGlasses[:,:,0:3]
  origGlassesHeight, origGlassesWidth = imgGlasses.shape[:2]
      
  video_capture = cv2.VideoCapture(0)
  
  while True:
      # Capture frame-by-frame
      ret, frame = video_capture.read()
  
      gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
  
      faces = face_cascade.detectMultiScale(gray, 1.3, 5)
      for (x,y,w,h) in faces:
          #cv2.rectangle(frame,(x,y),(x+w,y+h),(255,0,0),2)
              roi_gray = gray[y:y+h, x:x+w]
              roi_color = frame[y:y+h, x:x+w]
              
              eyes = eye_cascade.detectMultiScale(roi_gray)
              for (ex,ey,ew,eh) in eyes:
              cv2.rectangle(roi_color,(ex,ey),(ex+ew,ey+eh),(0,255,0),2)
                  
          for (ex, ey, ew, eh) in eyes:
              glassesWidth = 3*ew
              glassesHeight = glassesWidth * origGlassesHeight / origGlassesWidth
              
              # Center the glasses on the bottom of the nose
              x1 = ex - (glassesWidth/4)
              x2 = ex + ew + (glassesWidth/4)
              y1 = ey + eh - (glassesHeight/2)
              y2 = ey + eh + (glassesHeight/2)
                       
              # Re-calculate the width and height of the glasses image
              glassesWidth = x2 - x1
              glassesHeight = y2 - y1
           
              # Re-size the original image and the masks to the glasses sizes
              # calcualted above
              glasses = cv2.resize(imgGlasses, (glassesWidth,glassesHeight), interpolation = cv2.INTER_AREA)
              mask = cv2.resize(orig_mask, (glassesWidth,glassesHeight), interpolation = cv2.INTER_AREA)
              mask_inv = cv2.resize(orig_mask_inv, (glassesWidth,glassesHeight), interpolation = cv2.INTER_AREA)
           
              # take ROI for glasses from background equal to size of glasses image
              roi = roi_color[y1:y2, x1:x2]
           
                  # roi_bg contains the original image only where the glasses is not
                  # in the region that is the size of the glasses.
              roi_bg = cv2.bitwise_and(roi,roi,mask = mask_inv)
           
                  # roi_fg contains the image of the glasses only where the glasses is
              roi_fg = cv2.bitwise_and(glasses,glasses,mask = mask)
           
                  # join the roi_bg and roi_fg
              dst = cv2.add(roi_bg,roi_fg)
           
                  # place the joined image, saved to dst back over the original image
              roi_color[y1:y2, x1:x2] = dst
           
              break
  </code></pre>
  <p>I get the following error while trying to run the program and I have no idea how to fix this -</p>
  <blockquote>
  <p>OpenCV Error: Assertion failed ((mask.type() == CV_8UC1 || mask.type()
  == CV_8SC1)) in binary_op, file /home/user/opencv-2.4.10/modules/core/src/arithm.cpp, line 1035</p>
  <p>Traceback (most recent call last):   File &quot;main_eye.py&quot;, line 86, in
  </p>
  <p>roi_bg = cv2.bitwise_and(roi,roi,mask = mask_inv) cv2.error: /home/user/opencv-2.4.10/modules/core/src/arithm.cpp:1035: error:
  (-215) (mask.type() == CV_8UC1 || mask.type() == CV_8SC1) in function
  binary_op</p>
  </blockquote>