Processing saveFrame -- watch out... saves a TIFF everytime draw() runs if you run this as is!

saveFrame.pde

color[] cols = new color[2];
int c = 0;

void setup() {
  size(100, 100);
  cols[0] = color(255, 0, 0);
  cols[1] = color(0, 0, 255);
}

void draw() {
  background(cols[c]);
  c = 1 - c;
  saveFrame();
}