PImage myImage; //define an image object
myImage = loadImage("memorial.jpg"); //load it
size(myImage.width,myImage.height); //size it to fit the window
image(myImage, 0,0); //display the image
// convert the image to grayscale
filter(GRAY);
color white = color(255,255,255); //define white
color black = color(0,0,0); //define black
//extract edges
for(int y=0; y<myImage.height-1; y++) //for all pixels in y
  for(int x=0; x<myImage.width-1; x++){ //for all pixels in x
    color thisPixel = get(x,y); //get a pixel’s color
    color nextPixel = get(x+1,y); //get the next pixel’s color
    int ra = int(red(thisPixel)); //extract the red value
    int rb = int(red(nextPixel)); //extract the red of the next
    if(abs(ra-rb)>6) //if they are different
      set(x,y,black); //set the pixel’s color black
    else
      set(x,y,white); //else to white
  }
save("memorial_edge.jpg"); // save the image as a file