code: public static GrayS16 invert(GrayS16 input, int max , GrayS16 output) {
  		output = InputSanityCheck.checkDeclare(input, output);
  
  		ImplGrayImageOps.invert(input,max,output);
  
  		return output;
  	}
docs: <p>
  Inverts the image's intensity:<br>
  O<sub>x,y</sub> = max - I<sub>x,y</sub><br>
  </p>
  
  @param input  Input image. Not modified.
  @param output If not null, the output image.  If null a new image is declared and returned.  Modified.
  @return Output image.