title: clearing the image in a picturebox
body: <p>I have a form with a picturebox that will allow to draw a free hand picture.</p>
  
  <p>I added the initialization of the image in the <code>form_load</code> and the click event of the clear button. When I click the clear button the image is cleared and at the mouse move on the picturebox the last drawned image will shown.</p>
  
  <p>My question is, how can I validate the picturebox whether it is empty or not?
  Just that I don't want to permit to save an empty image.</p>