Resize and compress images on upload.

I’m looking for recommendations for an auto behind the scenes image compression and resizing plugin. My client doesn’t have Photoshop. I’m looking for a solution that I will not have to train them on. Preferably one that works behind the scenes. Their images 4896x3672px @ 350 res. That would quickly fill up the server space at 50+ megs per image not to mention the bandwidth!

I need to compress them by at least 50% and resize them to a max width 800 height 600.

Are there any plugins that will do that and not leave the original big azz file on the server?

Thanks