Resizing all images

I have just changed the theme on my blog, and because of a small page width, it breaks the layout. Most of my earlier images (attached in posts) are around 600px in width, and now I need to resize all of them them proportionately to 450px. How do I resize them all at one shot? Is there a plugin for this?

Rename image uploads with width in filename

I am attempting to change the name format that WordPress uses to rename uploaded files. For example, when I upload an image with filename cat-picture.jpg WordPress will create scaled versions and rename the filename to variations of cat-picture-{WIDTHxHEIGHT}.jpg. Is there a way I am able to move this width & height attribute to the beginning of the filename so instead I get variations of {WIDTHxHEIGHT}-cat-picture.jpg? So, in the context of this example, I’d like the filename to be renamed to 600x400-cat-picture.jpg. Thoughts?