[Answered ]-Doing some processing locally before uploading

This sort of thing was quite possible in the past with the help of Java applets. In fact, I built one of the first applets to do so. It could resize images on the fly or compress any file before update but I digress. Nowadays applets are not widely supported in browsers.

You do have the option of using one of several javascript file uploaders that allow loading an image into a canvas. See this excellent tutorial on MDN on how to use the canvas. This QA explains how to load an image into the canvas.