title: Change origin of image coordinate system to bottom left instead of default top left
body: <p>Is there a simple way of changing the origin of image co-ordinate system of OpenCV to bottom left? Using <code>numpy</code> for example? I am using OpenCv 2.4.12 and Python 2.7.</p>
  
  <p>Related: <a href="https://stackoverflow.com/questions/31527016/numpy-flipped-coordinate-system">Numpy flipped coordinate system</a>, but this talks about just display. I want something which I can use consistently in my algorithm.</p>
  
  <p>Update:</p>
  
  <pre><code>def imread(*args, **kwargs):
      img = plt.imread(*args, **kwargs)
      img = np.flipud(img)
      return img      
  #read reference image using cv2.imread
  imref=cv2.imread('D:\\users\\gayathri\\all\\new\\CoilA\\Resized_Results\\coilA_1.png',-1)
  cv2.circle(imref, (0,0),30,(0,0,255),2,8,0)
  cv2.imshow('imref',imref)
  
  #read the same image using imread function
  im=imread('D:\\users\\gayathri\\all\\new\\CoilA\\Resized_Results\\coilA_1.png',-1)
  img= im.copy()
  cv2.circle(img, (0,0),30,(0,0,255),2,8,0)
  cv2.imshow('img',img)
  </code></pre>
  
  <p>Image read using cv2.imread:
  <a href="https://i.stack.imgur.com/Hw4oi.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Hw4oi.png" alt="original image"></a></p>
  
  <p>Image flipped using imread function:
  <a href="https://i.stack.imgur.com/chRJ6.png" rel="noreferrer"><img src="https://i.stack.imgur.com/chRJ6.png" alt="flipped"></a></p>
  
  <p>As seen the circle is drawn at the origin on upper left corner in both original and flipped image. But the image looks flipped which I do not desire.</p>