title: Display filter C#
body: <p>It's a little hard to explain what I need but i'll try:</p>
  
  <p>I need to write application (winform) which will be some kind of filter to image/other forms behind it. With one exception - all behind form should looks as is except of red (for example) color, which have to be replaced to any other specified color, white for example.</p>
  
  <p>So let's imagine I have opened windows Word with few lines of text. With red and black letters.
  So when i place my application above this text - it should "filter" red symbols and fill them to white.</p>
  
  <p>So as i understand this task: i have to snap area behind the form, then process it (replace colors) and after draw this image on my form body.</p>
  
  <p>Any links or keywords for solution?</p>
  
  <p>UPD:</p>
  
  <p>so - this is my final solution:</p>
  
  <ol>
  <li>do form transparent (using TransparencyKey and BackColor properties)</li>
  <li>place picturebox over the form</li>
  <li>when we need to update image in picturebox - we replace current image with pictureBox1.Image = null;, then refreshing form with (this.Refresh()) and do new snapshot</li>
  </ol>
  
  <p>thanks for all ;-)</p>
  
  <p>UPD 2:
  <a href="http://dl.dropbox.com/u/4486681/result.png" rel="nofollow noreferrer">sample http://dl.dropbox.com/u/4486681/result.png</a></p>
  
  <p>UPD 3:
  here are <a href="http://dl.dropbox.com/u/4486681/filter/filter.7z" rel="nofollow noreferrer">sources</a></p>