code: public static int sum( GrayS32 img ) {
  
  		if( BoofConcurrency.USE_CONCURRENT ) {
  			return ImplImageStatistics_MT.sum(img);
  		} else {
  			return ImplImageStatistics.sum(img);
  		}
  	}
docs: <p>
  Returns the sum of all the pixels in the image.
  </p>
  
  @param img Input image. Not modified.