Fw: imagecreatefromjpeg()

Hi, I need to create thuimbnails from bigger image files. I tried to use the imagecreatefromjpeg() funktion, but it doesn't work. What can I do about that? Is it right, when I use the function like: $image = "image/imagename.jpg"; $source = imagecreatefromjpeg($source); later I want to resize the image by the imagecopyresized() function but what do all these functions return, and how fast are they working? If there is someone out there, whos able to help me, i would be very glad. Thanks Sascha