This has more value than education. I wish that I could use this as an editor to put finishing touches on images so web pages go faster for people with less bandwidth. Photoshop, GIMP, and ImageMagick can't do this. The quality slider is a blunt tool that applies to the whole image. It should be possible to define a quality mask, since things outside the field of view can safely be compressed more. But classic algorithms aren't good at determining what that is, plus jpeg isn't conventionally thought of as being the canvas.