code: function (inData, outData, width, height) {
          var c = 1 / 9;
          convolve3x3(inData, outData, width, height,
              [
                  [c, c, c],
                  [c, c, c],
                  [c, c, c]
              ]);
      }
docs: A 3x3 low-pass mean filter