gistfile1.php

<?php

$filename = "/Andy.jpg";
$min = 800;

list($width, $height) = getimagesize($filename);
$source = imagecreatefromjpeg($filename);

$max = max($height, $width);
if ($min != null && $min > $max) {

	$max = $min;
}


$target = imagecreatetruecolor($max, $max);
$white = imagecolorallocate($target, 255, 255, 255);
imagefill($target, 0, 0, $white);
	
	
imagecopyresized($target, $source, ($max - $width) / 2, ($max - $height) /2,0, 0,  $width, $height, $width, $height);
	
header('Content-type: image/png');
imagepng($target);
imagedestroy($source);
imagedestroy($target);