include and imagejpg() weird behavior - maybe header?

I have a function that resizes images. If I put it in the same php file that calles it it workes fine. Gives a nice thumbnail or whatever size I choose to display. If I however put it in a seperate file and include it and call it I get garbage and the following error: Warning: Cannot modify header information - headers already sent by (output started at /home/edal/public_html/album/image.php Here is the resize function (in file image.php): <? function resize($filepath,$nw = 50,$string = '') { header("Content-type: image/jpeg"); $im = imagecreatefromjpeg($filepath); $w = imagesx ($im); $h = imagesy ($im); $nh = round($h*$nw/$w,0); $newim = imagecreatetruecolor($nw,$nh); $black = imagecolorallocate($newim, 0, 0, 0); imagecopyresampled($newim,$im,0,0,0,0,$nw,$nh,$w,$h); imagestring($newim, 2, 5, 5, $string, $black); imagedestroy($im); return $newim; } ?> and the calling script: <?php include 'image.php'; $image = resize('Capri.jpg',200,'Capri'); imagejpeg($image); imagedestroy($image); ?> Any ideas? Oli