Zmenšování obrázků přes GET s přímým výstupem vypisuje chybu

<?php
$a = $_GET["a"]; //album
$o = $_GET["o"]; //obrazek
$s = $_GET["s"]; //size

if(file_exists("../core/photos/".$a."/big/".$o))
{
$file = "../core/photos/".$a."/big/".$o;
header('Content-Type: image/jpeg');

list($width, $height) = getimagesize($file);
$pomer = ($width/$height);

if($s=="big" or $s==""){$vystup = imagecreatetruecolor($width, $height);
    $smaller = imagecreatefromjpeg($file);
    imagecopyresized($vystup, $smaller, 0, 0, 0, 0, $width, $height, $width, $height);}

if($s=="medium"){$newheight = (500/$pomer);$vystup = imagecreatetruecolor(800, $newheight);
    $smaller = imagecreatefromjpeg($file);
    imagecopyresized($vystup, $smaller, 0, 0, 0, 0, 500, $newheight, $width, $height);}

if($s=="small"){$newheight = (230/$pomer);$vystup = imagecreatetruecolor(230, $newheight);
    $smaller = imagecreatefromjpeg($file);
    imagecopyresized($vystup, $smaller, 0, 0, 0, 0, 230, $newheight, $width, $height);}

imagejpeg($vystup);
}
else
{
    echo "Image <strong>".$o."</strong> from <strong>".$a."</strong> does not exists.";
}
?>