var x1 = 0;

var x2;

​

var scrollSpeed = 2;

​

function preload(){

    bgImg = loadImage("bg.png");

}

​

function setup() { 

  createCanvas(400, 400);

  x2 = width;

} 

​

function draw() { 

    image(bgImg, x1, 0, width, height);

  image(bgImg, x2, 0, width, height);

  x1 -= scrollSpeed;

  x2 -= scrollSpeed;

  if (x1 < -width){

    x1 = width;

  }

  if (x2 < -width){

    x2 = width;

  }

}