Viewing file:  evercookie_png.php (1.9 KB) -rw-r--r--
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<?php
/* evercookie, by samy kamkar, 09/20/2010
* http://samy.pl : code@samy.pl
*
* This is the server-side variable PNG generator for evercookie.
* If an HTTP cookie is passed, the cookie data gets converted into
* RGB-values in a PNG image. The PNG image is printed out with a
* 20-year cache expiration date.
*
* If for any reason this file is accessed again WITHOUT the cookie,
* as in the user deleted their cookie, the code returns back with
* a forced 'Not Modified' meaning the browser should look at its
* cache for the image.
*
* The client-side code then places the cached image in a canvas and
* reads it in pixel by pixel, converting the PNG back into a cookie.
*
* -samy kamkar
*/
// we get cookie name from current file name so remember about it when rename of this file will be required
include dirname(__FILE__) . DIRECTORY_SEPARATOR . '_cookie_name.php';
$cookie_name = evercookie_get_cookie_name(__FILE__);
// we don't have a cookie, user probably deleted it, force cache
if (empty($_COOKIE[$cookie_name])) {
if(!headers_sent()) {
header('HTTP/1.1 304 Not Modified');
}
exit;
}
// width of 200 means 600 bytes (3 RGB bytes per pixel)
$x = 200;
$y = 1;
$gd = imagecreatetruecolor($x, $y);
$data_arr = str_split($_COOKIE[$cookie_name]);
$x = 0;
$y = 0;
for ($i = 0, $i_count = count($data_arr); $i < $i_count; $i += 3) {
$red = isset($data_arr[$i]) ? ord($data_arr[$i]) : 0;
$green = isset($data_arr[$i+1]) ? ord($data_arr[$i+1]) : 0;
$blue = isset($data_arr[$i+2]) ? ord($data_arr[$i+2]) : 0;
$color = imagecolorallocate($gd, $red, $green, $blue);
imagesetpixel($gd, $x++, $y, $color);
}
if(!headers_sent()) {
header('Content-Type: image/png');
header('Last-Modified: Wed, 30 Jun 2010 21:36:48 GMT');
header('Expires: Tue, 31 Dec 2030 23:30:45 GMT');
header('Cache-Control: private, max-age=630720000');
}
// boom. headshot.
imagepng($gd);
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