Resizing an image

Hi everyone, Image processing is a part of Php language completely unknown to me :-(. So there is my task: I need to process an uploaded image. We allow uploading of gif, jpeg, and png images. If an image is wider than 600px, it should be proportionally resized to the width of 600px. Yes, I've just read about ImageCopyResampled(). My questions are: 1. what are the restrictions of ImageCopyResampled()? Can I make a jpg image from a jpg one, and a png image from a png one? And what about gif's? 2. I don't need to output the image as the script output, I need to upload it as a file (replacing the uploaded larger file). Could I make it with fwrite and then copy it to the server? All of the examples give header("image/jpeg")... Thanks! -- With best regards from Ukraine, Andre Skype: Francophile Twitter: http://twitter.com/m_elensule Facebook: http://facebook.com/menelion