code: function lanczos(x, a) {
  
          // Lanczos is sinc(x) * sinc(x / a) for -a < x < a ...
          if (-a < x && x < a)
              return sinc(x) * sinc(x / a);
  
          // ... and 0 otherwise
          return 0;
  
      }
docs: Calculates the value of the Lanczos kernal at point x for a given window
  size. See: https://en.wikipedia.org/wiki/Lanczos_resampling
  
  @private
  @param {Number} x
  The point at which the value of the Lanczos kernel should be
  computed.
  
  @param {Number} a
  The window size to use for the Lanczos kernel.
  
  @returns {Number}
  The value of the Lanczos kernel at the given point for the given
  window size.