StackBlur backgrounds

Theme component
10

Seems promising, but I get:
Uncaught ReferenceError: assignment to undeclared variable img

          var blur = $("#background_b").data("blur");
          img = new Image();
          c = document.getElementById("background_b");
          ctx = c.getContext("2d");
          w = window.innerWidth;
          h = window.innerHeight;

I think you meant to use commas instead of semicolons here.