mix

PImage tmp;
PImage[] img = new PImage[2];
int x, y, w, h, r=100, r2=100;
int num = int(map(r2,0,100,10000,2000));

void setup() {
  img[0] = loadImage("3.jpg");
  img[1] = loadImage("4.jpg");
  size(img[0].width, img[0].height);
  initStuff();
}

void draw() {
}

void mouseReleased() {
  background(255);
  initStuff();
}

void keyPressed() {
  save(num+".jpg");
}

void doStuff(int v, float v1, float v2) {
  w = (int) random(r2, 3*r2);
  h = (int) random(r2, 3*r2);
  x = (int) random(v1, v2-w);
  y = (int) random(height-h);
  tmp = createImage(w, h, RGB);
  tmp.loadPixels();
  int c=0;
  for (int j=0; j<h; j++) {
    for (int i=0; i<w; i++) {
      tmp.pixels[c] = img[v].get(x+i, y+j);
      c++;
    }
  }
  tint(255, 100);
  image(tmp, x+random(-r, r), y+random(-r, r));
}

void initStuff() {
  for (int i=0; i<num; i++) {
    doStuff(0, 0, width/2);
    doStuff(1, width/2, width);
  }
}