title: Improve pre-processing for OCR/Image Recognition
body: <p>Currently i'm having a huge intrest in image processing and optical character recognition. After some basic recognition and some filters I decided to start on something more diffucult.</p>
  
  <p>I'm trying to read the value out of these captchas:
  <a href="http://img851.imageshack.us/img851/9579/57859946.png" rel="nofollow">http://img851.imageshack.us/img851/9579/57859946.png</a></p>
  
  <p>I have written some filters for pre-processing:
  - Replace Color (to White) 
    Remove blue lines 
    remove the lines that go trough the text (two)
  - Threshold image (255)</p>
  
  <p>Wich outputs an images like this;
  <a href="http://img232.imageshack.us/img232/2325/00i3q45j1zt.png" rel="nofollow">http://img232.imageshack.us/img232/2325/00i3q45j1zt.png</a></p>
  
  <p>As you can see there are holes in some letters. I first thought maybe it's better to leave the lines trough the letters but that made it worse. I'm using the tesseract OCR engine
  and I trained it using the Elephant font (The font the captcha uses). I also tried
  using other OCR engines like GOCR but it makes everything worse. With tesseract I now have a recognition of 20%. I'm coding in C# (.NET 4.0).</p>
  
  <p>The captcha is generated by a software package named PHPCaptcha. </p>
  
  <p>Now my question is:
  Is there any algorithm or tick to fill up the holes in the letters? And is there any other way to get a better recognition?</p>
  
  <p>I'm excited to hear from you guys :)</p>
  
  <p>Greetings,</p>