PImage myImage; //define an image object
  PImage cpImage; //define a copy image
  void setup(){
    myImage = loadImage("memorial.jpg"); //load it
    cpImage = loadImage("memorial.jpg"); //load the copy
    size(myImage.width,myImage.height); //size it to fit the window
    image(myImage, 0,0); //display the image
    loadPixels(); //load the pixels
  }
  //**********
  void draw(){
  }
  //********* drag to simulate a paint brush
  void mouseDragged(){
    for(int y=mouseY-10; y<mouseY+10; y++) //for a 10x10 brush area
      for(int x=mouseX-10; x<mouseX+10; x++){
        int xx = constrain(x,0,width-1); //do not exceed the screen
        int yy = constrain(y,0,height-1);
        //read from the copy and update the image
        pixels[yy*width+xx] = cpImage.pixels[yy*width+xx]^0x0000FF;
        //invert blue
      }
    //copy the two images
    myImage.copy(cpImage, 0,0,width,height,0,0,width,height);
    updatePixels(); //update to see the changes
  }