Automatically create thumbnails of JPG images to your required size. Great for creating a thumbnail of an image automatically when a user uploads a 2.5MB 3500x2500 picture and you want to have a thumbnail on the website of a specific dimension. This version only does JPGs.

<?php
function thumbnail($i,$nw,$p,$nn) { 
    $img=imagecreatefromjpeg("$i"); 
    $ow=imagesx($img); 
    $oh=imagesy($img); 
    $scale=$nw/$ow;
    $nh=ceil($oh*$scale);
    $newimg=imagecreate($nw,$nh); 
    imagecopyresized($newimg,$img,0,0,0,0,$nw,$nh,$ow,$oh);
    imagejpeg($newimg, $p.$nn); 
    return true; 
}

#thumbnail(filetouse,newwidth,newpath,newname);
thumbnail("/img/x.jpg",100,"/img/thm/","xt.jpg");
?>