如何使用requestAnimationFrame对画布中的图像进行动画处理?

时间:2018-09-21 06:48:03

标签: javascript css html5-canvas requestanimationframe

我想使用HTML5画布中的requestAnimationFrame从左向右移动图像。

let canvas= document.querySelector("canvas");
canvas.width=window.innerWidth;
canvas.height=window.innerHeight;
let c= canvas.getContext('2d');

let image= new Image();
image.src="./balloon.png";

let x=0;

function draw(){
    image.addEventListener("load",()=>{
        c.drawImage(image,x,0);
    });  
}

function update(){
    x+=1;
    draw();
}

function animate(){
    c.clearRect(0,0,canvas.width,canvas.height);
    requestAnimationFrame(animate);
    update();  
}
animate();

通常图像正在加载,但是当我尝试在其中添加动画帧时,图像消失了。

1 个答案:

答案 0 :(得分:1)

您只需加载一次图像。

let canvas= document.querySelector("canvas");
canvas.width=window.innerWidth;
canvas.height=window.innerHeight;
let c= canvas.getContext('2d');

let image= new Image();
image.src="https://s3-us-west-2.amazonaws.com/s.cdpn.io/222579/darwin300.jpg";

let x=0;

 image.addEventListener("load",()=>{
        c.drawImage(image,x,0);
    });  

function draw(){
 
        c.drawImage(image,x,0);
  
}

function update(){
    x+=1;
    draw();
}


function animate(){
    c.clearRect(0,0,canvas.width,canvas.height);
    requestAnimationFrame(animate);
    update();  
}
animate();
<canvas></canvas>