title: how to get touch coordinates in an image then draw a markup icon and its content in a popover view
body: <p>I would like to built an iPhone/iPad application to show large images (in a scrollView or something else which support dragging and zooming) that allow user to:</p>
  
  <ul>
  <li>Touch some where in the image to markup and leave comment</li>
  <li>User can tap on that markup icon/button to view comment in a popOverView</li>
  <li>Edit comment or remove that markup</li>
  </ul>
  
  <p>So I want to ask that:</p>
  
  <ul>
  <li>How can I get the touch coordinates in image (not screen)?</li>
  <li>How can I draw a markup icon/button at touch point in the image and it would follow image even when dragging, zooming since the image is really large, maybe up to 8000x6000 pixels?</li>
  <li>How can I display comment/note when user touch on markup icon/button in a view like popOverview in iPad?</li>
  <li>Save and load these information.</li>
  </ul>
  
  <p>It is nearly similar to tagging functionality of Facebook App in iPhone.</p>
  
  <p>Any help is appreciated, thank in advance!</p>