class CaptchaSecurityImages {

var $font = 'C:/WINNT/Fonts/arial.ttf';

function generateCode($characters) {

$possible = '23456789bcdfghjkmnpqrstvwxyz';

$code = '';

$i = 0;

while ($i < $characters) {

$code .= substr($possible, mt_rand(0, strlen($possible)-1), 1);

$i++;

return $code;

function CaptchaSecurityImages($width='120',$height='40',$characters='6') {

$code = $this->generateCode($characters);

$font_size = $height * 0.75;

$image = imagecreate($width, $height) or die('Cannot initialize new GD image stream');

$background_color = imagecolorallocate($image, 255, 255, 255);

$text_color = imagecolorallocate($image, 20, 40, 100);

$noise_color = imagecolorallocate($image, 100, 120, 180);

for( $i=0; $i<($width*$height)/3; $i++ ) {

imagefilledellipse($image, mt_rand(0,$width), mt_rand(0,$height), 1, 1, $noise_color);

for( $i=0; $i<($width*$height)/150; $i++ ) {

imageline($image, mt_rand(0,$width), mt_rand(0,$height), mt_rand(0,$width), mt_rand(0,$height), $noise_color);

$textbox = imagettfbbox($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');

header('Content-Type: image/jpeg');

imagejpeg($image);

imagedestroy($image);

$_SESSION['security_code'] = $code;

$width = isset($_GET['width']) && $_GET['width'] < 600 ? $_GET['width'] : '120';

$height = isset($_GET['height']) && $_GET['height'] < 200 ? $_GET['height'] : '40';

$characters = isset($_GET['characters']) && $_GET['characters'] > 2 ? $_GET['characters'] : '6';

$captcha = new CaptchaSecurityImages($width,$height,$characters);

After running the program you will get the following output

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