这不断得到一条错误消息,说它不是一个功能,请帮助!!
var ctx = document.getElementById('canvas').getContext('2d');
HTML：
<html>
<head>
<title>Canvas Race</title>
<script src="jquery-2.2.3.js"></script>
<style type="text/css">
canvas {
border: 1px solid black;
background-image: url("http://www.gamefromscratch.com/image.axd?picture=road2048v2.png");
background-size: 200px 300px;
background-position-y: -81px;
}
</style>
</head>
<body>
<div id="canvas">
<canvas id="myCanvas" width="1100" height="150" ></canvas>
</div>
<div id="winner"></div>
</body>
</html>
使用Javascript：
<script type="text/javascript">
var blueCar = new Image();
var redCar = new Image();
// images
function image(){
blueCar.src = "http://worldartsme.com/images/car-top-view-clipart-1.jpg";
redCar.src = "http://images.clipartpanda.com/car-clipart-top-view-free-vector-red-racing-car-top-view_099252_Red_racing_car_top_view.png";
window.requestAnimationFrame(draw);
}
function draw() {
var ctx = document.getElementById('canvas').getContext('2d');
ctx.globalCompositeOperation = 'destination-over';
//blue car
ctx.drawImage(blueCar,10,100,100);
}
image();
</script>
我已经四处寻找,但是我没有找到任何有效的东西;我不知道它是否必须对我的jquery做任何事情.
解决方法
你在那里引用了那个id的div …
DIV没有像.getContext()这样的属性方法,所以这里是工作部分：
DIV没有像.getContext()这样的属性方法,所以这里是工作部分：
var blueCar = new Image();
var redCar = new Image();
// images
function image(){
blueCar.src = "http://worldartsme.com/images/car-top-view-clipart-1.jpg";
redCar.src = "http://images.clipartpanda.com/car-clipart-top-view-free-vector-red-racing-car-top-view_099252_Red_racing_car_top_view.png";
window.requestAnimationFrame(draw);
}
function draw() {
var ctx = document.getElementById('canvas').getContext('2d');
ctx.globalCompositeOperation = 'destination-over';
//blue car
ctx.drawImage(blueCar,100);
}
image();
<html>
<head>
<title>Canvas Race</title>
<script src="jquery-2.2.3.js"></script>
<style type="text/css">
canvas {
border: 1px solid black;
background-image: url("http://www.gamefromscratch.com/image.axd?picture=road2048v2.png");
background-size: 200px 300px;
background-position-y: -81px;
}
</style>
</head>
<body>
<div id="mycanvas">
<canvas id="canvas" width="1100" height="150" ></canvas>
</div>
<div id="winner"></div>
</body>
</html>
