<?php
$w = (int) $_GET['w'];
$h = (int) $_GET['h'];
$c = $_GET['c'];
if($w=='' || $h=='' || $c=='') die('error');
$image = imagecreatetruecolor($w,$h);
imagefill($image, 0, 0, '0x'.$c);
header('Content-type: image/png');
imagepng($image);
imagedestroy($image);
?>