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Revision: 42026
at February 26, 2011 02:39 by stz184
Initial Code 
session_start();
header("Content-type: image/png");
$width = 146;
$height = 30;

$im = @imagecreate($width, $height)or die("Cannot Initialize new GD image stream");

imagecolorallocate($im, 255, 250, 255);
$noise_color = imagecolorallocate($im, 207, 239, 250);
for($i=0; $i<($width*$height)/3; $i++) {
	imagefilledellipse($im, mt_rand(0,$width), mt_rand(0,$height), 1, 1, $noise_color);
}

/* generate random lines in background */
for($i=0; $i<($width*$height)/150; $i++ ) {
 imageline($im, mt_rand(0,$width), mt_rand(0,$height), mt_rand(0,$width), mt_rand(0,$height), $noise_color);
}

$text_color[0] = imagecolorallocate($im, 255, 0, 0);
$text_color[1] = imagecolorallocate($im, 51, 166, 207);

$text = mb_substr(uniqid(mt_rand(), true), 0, 6);
unset($_SESSION['captcha']);
$_SESSION['captcha']['blue'] = $_SESSION['captcha']['red'] = '';

for($j = 0; $j < mb_strlen($text); $j++) {
	imagettftext($im, 20, 0, 5+($j*23), 24, $text_color[$j%2], './offshore.ttf', $text[$j]);
	if(($j%2) == 1) {
		$_SESSION['captcha']['blue'] .= $text[$j];
	}
	else {
		$_SESSION['captcha']['red'] .= $text[$j];
	}
}
imagepng($im);
imagedestroy($im);
Initial URL 
http://vladimir-ivanov.net
Initial Description 
Tell the users to enter only the red or only the blue digits, not everything they see.
Most bots will try to enter everything, displayed on the images.
To check is captcha code entered correctly, use $_SESSION['captcha']['red'] to check the red digits only and $_SESSION['captcha']['blue'] to check the blue digits only. Good luck !
Initial Title 
Captcha with color protection
Initial Tags 

                                

                                                            

                                    

                                        

                                        Initial Language
                                        

                                    

                                    
PHP