title: How to add text to an image?
body: <p>In my project I use iText to generate a PDF document.</p>
  
  <p>Suppose that the height of a page measures 500pt (1 user unit = 1 point), and that I write some text to the page, followed by an image.</p>
  
  <p>If the content and the image require less than 450pt, the text preceded the image.
  If the content and the image exceed 450pt, the text is forwarded to the next page.</p>
  
  <p>My question is: how can I obtain the remaining available space before writing an image?</p>