How to save images in this way?

Question

Currently I'm using PhpThumb to save images:

http://phpthumb.gxdlabs.com/

I already get a plugin to put watermarks:

http://phpthumb.gxdlabs.com/forums/topic/watermark-plugin#post-115

Now, I would like to do a plugin to save images like that:

The example can be just with php. Which is the best way to define a specific size and then put parts of the image in the empty space?

and