void setup() {

 size(512, 512);
   background(0);
   PImage img = loadImage("Lenna.png");
   imageMode(CENTER);
   image(img, width/2, height/2);
   println("Width = " + img.width + ", Height = " + img.height);

 // Print the RGB values of pixel[0]
   loadPixels();
   color darkBlue = color(0, 51, 76);
   color lightBlue = color(112, 150, 158);
   color red = color(217, 26, 33);
   color yellow = color(252, 227, 166);
 

 for (int i = 0; i < pixels.length; i++) {
   // get and change the value of each pixel
   color pixelValue = pixels[i];
   float r = red(pixelValue);
   float g = green(pixelValue);
   float b = blue(pixelValue);
   float total = r + g + b;

 if (total < 182) {
   pixels[i] = darkBlue;
 } else if (total < 182*2) {
   pixels[i] = lightBlue;
 } else if (total < 182*3) {
   pixels[i] = yellow;
 } else {
   pixels[i] = red;
 }
   }
   updatePixels();
   color c = pixels[0];
   println("R = " + red(c) + ", G = " + green(c) + ", B = " + blue(c));
} // setup()