code: public static void stdDev(Planar<GrayU8> input, GrayU8 output, @Nullable GrayU8 avg) {
  		stdDev(input,output,avg,0,input.getNumBands() - 1);
  	}
docs: Computes the standard deviation for each pixel across all bands in the {@link Planar}
  image.
  @param input     Planar image - not modified
  @param output    Gray scale image containing average pixel values - modified
  @param avg       Input Gray scale image containing average image.  Can be null