Images : Upload, Create Thumbnail, Manipulate

[SDB]

I want to write a function to allow the user to upload images, create a number of different thumbnails of various sizes, and to manipulate the thumbnails (putting rounded corners on them, watermarks, etc).

Anyone know of any good tutorials, etc?

[Dismounted]

You would most likely be wanting to look at the PHP GD Functions. They are the functions relating to image manipulation within PHP (unless if you use ImageMagick of course).