docs: public static GrayS32 average( Planar<GrayS32> input , GrayS32 output ) {
  		if (output == null) {
  			output = new GrayS32(input.width, input.height);
  		} else {
  			output.reshape(input.width,input.height);
  		}
  
  		if( BoofConcurrency.USE_CONCURRENT ) {
  			ImplConvertPlanarToGray_MT.average(input,output);
  		} else {
  			ImplConvertPlanarToGray.average(input,output);
  		}
  
  		return output;
  	}