<?php
   
class CaptchaSecurityImages { 
   var $font = './monofont.ttf';    

   function CaptchaSecurityImages($width='48',$height='19',$characters) {
      $code = $characters;
      /* font size will be 90% of the image height */
      $font_size = $height * 0.80;
      $image = imagecreate($width, $height) or die('Cannot initialize new GD image stream');
      /* set the colours */
      $background_color = imagecolorallocate($image, 255, 255, 255);
      $text_color = imagecolorallocate($image, 0, 0, 0);
      $noise_color = imagecolorallocate($image, 140, 140, 140);
      /* generate random dots in background */
      for( $i=0; $i<($width*$height)/3; $i++ ) {
         imagefilledellipse($image, mt_rand(0,$width), mt_rand(0,$height), 1, 1, $noise_color);
      }
      /* generate random lines in background */
      for( $i=0; $i<($width*$height)/100; $i++ ) {
         imageline($image, mt_rand(0,$width), mt_rand(0,$height), mt_rand(0,$width), mt_rand(0,$height), $noise_color);
      }
      /* create textbox and add text */
      $textbox = imagettfbbox($font_size, 0, $this->font, $code) or die('Error in imagettfbbox function');
      $x = ($width - $textbox[4])/2;
      $y = ($height - $textbox[5])/2;
      imagettftext($image, $font_size, 0, $x, $y, $text_color, $this->font , $code) or die('Error in imagettftext function');
      /* output captcha image to browser */
      header('Content-Type: image/jpeg');
      imagejpeg($image);
      imagedestroy($image);
   }
 
}

$width = "50";
$height = "22";
$captcha = new CaptchaSecurityImages($width,$height,$_GET['c']);

?>