What's the technology that Gravatar uses for us to resize our images when we upload it?
I'm pretty sure it's just js. Unless they are doing Agile for their front-end and already went through another cycle. I remember looking at it when I was doing Wordpress stuff a couple of years back.
Edit to answer question: No, I don't think you need the canvas element unless they have significantly changed their code-base in the last year.
I would think it's ImageMagick. Gravatar has been around for quite a while.