download image in php

// Output and free from memory
header('Content-Type: image/png');
//header('Content-Type: image/jpeg');
header("Content-Transfer-Encoding: binary");
header('Content-Description: File Transfer');
header('Content-Type: ' ,'pdf');
//header('Content-Length: ' . $file_size);
header('Content-Disposition: attachment; filename=' . $dest);
header('Content-Type: image/png');