title: captcha image is not visible in php
body: <p>I have pre installed GD library and Freetype library in centos server.
  I am not able to see captcha image.</p>
  
  <p>ERROR:</p>
  
  <pre><code>Call to undefined function imagettfbbox() in /path/public_html/captcha/securimage.php
  </code></pre>
  
  <p>What could be the reason?</p>
  
  <p>Thanks.</p>