这是因为啥啊？？？求教"Uncaught InvalidStateError: Failed to execute 'drawImage' on 'CanvasRenderingContext2D': The HTMLImageElement provided is in the 'broken' state."

var can1;

var can2;

var ctx1;

var ctx2;

var canWidth;

var canHeight;

var lastTime;

var deltaTime;

var bgPic = new Image();

document.body.onload = game;

function game()

{

init();

lastTime = Date.now();

deltaTime = 0;

gameloop();

}

function init()

{

//获得canvas can text

can1 = document.getElementById("canvas1");

ctx1 = can1.getContext('2d');

can2 = document.getElementById("canvas2");

ctx2 = can2.getContext('2d');

bgPic.src = "./src/background.jpg";

canWidth = can1.width;

canHeight = can1.height;

}

function gameloop()

{

window.requestAnimationFrame(gameloop);

var now = Date.now();

deltaTime=now - lastTime;

lastTime = now;

drawBackground();

}