title: Assertion failure : size.width>0 && size.height>0 in function imshow
body: <p>i am using opencv2 and python on raspberry pi. and i am new with python and opencv. i tried to read a jpeg image and display image it shows the following error: </p>
  
  <pre><code>/home/pi/opencv-2.4.9/modules/highgui/src/window.cpp:269: \
    error: (-215) size.width&gt;0 &amp;&amp;  size.height&gt;0 in function imshow.
  </code></pre>
  
  <p>and the code is: </p>
  
  <pre><code>import cv2
  # windows to display image
  cv2.namedWindow("Image")
  # read image
  image = cv2.imread('home/pi/bibek/book/test_set/bbb.jpeg')
  # show image
  cv2.imshow("Image", image)
  # exit at closing of window
  cv2.waitKey(0)
  cv2.destroyAllWindows()
  </code></pre>