<?php
$nw=100; //размеры
$nh=100;
$file=htmlspecialchars($_GET['file']);
list(, , $type,)=getimagesize($file);
if($type==1) { $func='imagecreatefromgif'; }
if($type==2) { $func='imagecreatefromjpeg'; }
if($type==3) { $func='imagecreatefrompng'; }
if($type)
{
$scr= $func($file);
$scrnew = imagecreatetruecolor($nw,$nh);
imagecopyresized($scrnew,$scr,0,0,0,0,$nw,$nh,imagesx($scr),imagesy($scr));
header ('Content-type: image/gif');
imagegif($scrnew); }
?>