code: function boxBlur(scl, tcl, w, h, r) {
      for (var i = 0, l = scl.length; i < l; i++) { tcl[i] = scl[i]; }
      boxBlurH(tcl, scl, w, h, r);
      boxBlurV(scl, tcl, w, h, r);
  }
docs: Perform a 2D box blur by doing a 1D box blur in two directions.
  
  Uses the same parameters as gaussblur().