signature_creator.php:
<?php
$images[one] = 'imageOne.gif';
$images[two] = 'imageTwo.gif';
$images[three] = 'imageThree.gif';
if($_SERVER['PATH_INFO']=='/download') {
if(!is_numeric($_POST[position_y]) || !is_numeric($_POST[position_x])) die('ERROR LOL!');
if(!$im = imagecreatefromgif($images[$_POST[image]])) die('ERROR LOL!');
$bg = imagecreatefromgif('signature.gif');
list($imw, $imh) = getimagesize($images[$_POST[image]]);
imagecopymerge($bg, $im, $_POST[position_x], $_POST[position_y], 0, 0, $imw, $imh, 100);
header('Content-Type: image/gif');
header ("Content-Disposition: attachment; filename=sig.gif");
imagegif($bg);
exit;
}
?>
<html>
<head>
<title>Signature Editor</title>
</head>
<body style="text-align: center;">
<form method="POST" action="signature_creator.php/download">
Select your image: <br />
<input name="image" value="one" type="radio" /> <img src="imageOne.gif" /> <br />
<input name="image" value="two" type="radio" /> <img src="imageTwo.gif" /> <br />
<input name="image" value="three" type="radio" /> <img src="imageThree.gif" /> <br />
<hr /><br />
Click to position image & download signature: <br />
<input type="image" name="position" src="signature.gif" >
</form>
</body>
</html>
I haven't tested it, and I'm not sure how secure it is.