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
loadPixels(); //get access to the array of pixels[]
for(int index=0;index<width*height;index++)
{
  int myPixel = pixels[index]; //get a pixel value
  int r = myPixel >> 16 & 0xFF; // get red(myPixel)
  int g = myPixel >> 8 & 0xFF; // get green(myPixel)
  int b = myPixel & 0xFF; // get blue(myPixel)
  int av= (g + b) /2; // average only green and blue
  if(av>128){      //e.g. if av is 00000000 00000000 00000000 11111111
    r = av << 16;       // Binary: 00000000 11111111 00000000 00000000
    g = av << 8;        // Binary: 00000000 00000000 11111111 00000000
    b = av;             // Binary: 00000000 00000000 00000000 11111111
    pixels[index] = r | g | b; //compose a color using bitwise OR
  }
}
updatePixels(); // see the result
save("memorial_altered.jpg"); // save the image as a file