int         len        = 5;
PGraphics[] pg         = new PGraphics[len];
int[]       xPos       = new int[len];
int         xPosGutter = 5;

void setup() {
    size(800, 600);
    for (int i = 0; i < len; i++) {
        pg[i] = createGraphics( (width/len)-xPosGutter, height );
        xPos[i] = (width/len) * i;
    }
}

void draw() {
    for (int i = 0; i < len; i++) {
        pg[i].beginDraw();
            pg[i].clear();
            pg[i].background( (i*25)+50 );
            pg[i].noStroke();
            pg[i].fill( (int)random(255), i*50, 0 );
            pg[i].ellipse((int)random(width/len), (int)random(height), 20, 20);
        pg[i].endDraw();

        image(pg[i], xPos[i], 0);
    }
}