public void filter(PixelImage pi)     {     Pixel[][] data = pi.getData();  // get image data              for (int row = 0; row < pi.getHeight(); row++)          {             for (int col = 0; col < pi.getWidth(); col++)              {                 int[] color={Pixel.RED, Pixel.BLUE, Pixel.GREEN};                                  for(int c=0;c<color.length;c++)                 {                     if(data[row][col].getComponentById(c)>0)                     {                         data[row][col].setComponentById(,c)=data[row][col].setComponentById(,c-20);                                              }                                      }                            }         }           // reset data into the PixelImage object pi         pi.setData(data);     }