title: Cannot read image using cv2.imread()
body: <p>I am trying to read an image and show it using <code>OpenCV</code> in Ubuntu, But for some reason it doesn't works. The file I am reading is placed in the same directory where the code resides but still it doesn't works. Can anybody tell me whats going on, Thank you</p>
  
  <p><strong>Error</strong></p>
  
  <pre><code>None
  Traceback (most recent call last):
    File "code.py", line 10, in &lt;module&gt;
      cv2.imshow('image', img)
  cv2.error: OpenCV(3.4.2) /io/opencv/modules/highgui/src/window.cpp:356: error: (-215:Assertion failed) size.width&gt;0 &amp;&amp; size.height&gt;0 in function 'imshow'
  </code></pre>
  
  <p><strong>code.py</strong></p>
  
  <pre><code>img = cv2.imread('sample1.jpg')
  print(img)
  cv2.imshow('image', img)
  </code></pre>