title: Construct a Numpy array from a hexadecimal string
body: <p>I have a hexadecimal string <code>"89-50-4E-47-0D-0A-1A-0A-00-00-00-0D-49"</code> to be specific this will contain the data of an image. </p>
  
  <p>I want to convert it to a Numpy array or possibly reconstruct an OpenCV image from the said data. </p>
  
  <p>The width and height will also be supplied so the dimensions of the Numpy array is known. </p>
  
  <p>How can I construct a Numpy array from the above string?</p>