title: simple measure over an image
body: <p>I need to take a measure (Euclidean distance) over a selected points on an image. In order to make this simpler I broke down all the process in steps:</p>
  
  <ol>
  <li>Taking/Loading a photo (with a known pattern in it) </li>
  <li>Recognizing the pattern to calibrate measure</li>
  <li>Selecting points "from" and "to" in order to measure the distance between them</li>
  </ol>
  
  <p>For my first iteration I will:</p>
  
  <ul>
  <li>load a picture (half of number 1),</li>
  <li>select the pattern manually (a rough approximation of number 2), and</li>
  <li>select point to measure distances between them.</li>
  </ul>
  
  <p>I'm just beginning with OpenCV; do I need it for my first iteration?</p>