code: @Override
  	protected void renderBitmapImage(BitmapMode mode, ImageBase image) {
  		switch( mode ) {
  			case UNSAFE: { // this application is configured to use double buffer and could ignore all other modes
  				VisualizeImageData.colorizeGradient(derivX, derivY, -1, bitmap, bitmapTmp);
  			} break;
  
  			case DOUBLE_BUFFER: {
  				VisualizeImageData.colorizeGradient(derivX, derivY, -1, bitmapWork, bitmapTmp);
  
  				if( bitmapLock.tryLock() ) {
  					try {
  						Bitmap tmp = bitmapWork;
  						bitmapWork = bitmap;
  						bitmap = tmp;
  					} finally {
  						bitmapLock.unlock();
  					}
  				}
  			} break;
  		}
  	}
docs: Override the default behavior and colorize gradient instead of converting input image.