Javascript Thumbnail Generator

I need a javascript to create a thumbnail from a full size photo. I’ve put up an example here: [login to view URL] I need something like this, this example is copyrighted so I can’t use that. The script has to work like this: I give the script an image url. The javascript displays the full size image and next to it an example of the thumbnail that will be created. The thumbnail size should be variable. I send the script the url with GET, like this: [login to view URL]://[login to view URL] I can drag my mouse over the full size image and select a part to create the thumbnail. This drag box should be in the thumbnail x and y ratio. After selecting I can click double on the selected area and the script will create a thumbnail using imagemagic and the script will write the thumbnail to the servers harddrive.