code: public static GrayU8 brighten(GrayU8 input, int beta, int max , GrayU8 output) {
  		output = InputSanityCheck.checkDeclare(input, output);
  
  		ImplGrayImageOps.brighten(input,beta,max,output);
  
  		return output;
  	}
docs: <p>
  Brightens the image's intensity:<br>
  O<sub>x,y</sub> = I<sub>x,y</sub> + beta<br>
  </p>
  <p>
  The image's intensity is clamped at 0 and max;
  </p>
  
  @param input  Input image. Not modified.
  @param beta   How much the image is brightened by.
  @param output If not null, the output image.  If null a new image is declared and returned.  Modified.
  @return Output image.