You can resize the tiff image as well as other type image.
I am sending code, i hope it will help to you...

<?php
$uploadedfile = $_FILES['uploadfile']['tmp_name'];

$src = imagecreatefromjpeg($uploadedfile);

list($width,$height)=getimagesize($uploadedfile);

$newwidth=600;
$newheight=($height/$width)*$newwidth;
$tmp=imagecreatetruecolor($newwidth,$newheight);

imagecopyresampled($tmp,$src,0,0,0,0,$newwidth,$newheight,$width,$height);

$filename = "images/". $_FILES['uploadfile']['name'];
imagejpeg($tmp,$filename,100);

imagedestroy($src);
imagedestroy($tmp);
?>

Thanks...