Well Apple sneaked this one in when we weren't looking. The latest version of Mac OS X (Panther or 10.3 to you) has built-in ability to manipulate images using Applescript. You can flip, rotate, pad, crop, scale and convert images all using simple Applescript commands. Now here's the fun part, both Userland Frontier and Radio can speak native Applescript. Anything you can do with Applescript you can do with Frontier or Radio.
So by way of a test my assetManager tool can now create thumbnails for moblog posts. I've built-in an Applescript routine into my Radio Userland tool and I'll release an update during Sunday for anyone who wants to give this a whirl. If you can't wait and if you are using Mac OS 10.3 click on this link to get a standalone Applescript file that scales images. As an aside, another cool feature of OS 10.3 is the ability to create Applescripts on-the-fly from an applescript:// URL action (try clicking the previous link)!
Well done Apple and well done Userland for supporting Applescript.