Canvas中如何绘制波浪花环，步骤方法是怎样-群英

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本篇内容介绍了“Canvas中如何绘制波浪花环，步骤方法是怎样”的有关知识，在实际项目的操作过程或是学习过程中，不少人都会遇到这样的问题，接下来就让小编带大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！

JS中的Canvas动画

几天没写博客了，今天又忙到很晚，教大家做一个波浪花环吧

效果图如上所示：

老规矩先把代码给大家，新建一个html文档(新建一个txt文本文档，把后缀名改为“ .html
”),以记事本打开，把复制好的代码粘贴进去，“ 保存 ”，退出，双击或右键选择浏览器打开。

祝大家前端学习愉快，在今后的日子中与君共勉

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
		body {
		  	background: #111;
		  	padding:0;
		  	margin:0;
			overflow:hidden;
		}
	</style>
</head>
<body>
	<div id="wrapper"></div>
</body>
<script>
(function(){
	'use strict';
	let wrapper, canvas, ctx, width, height, 
	Tau=Math.PI*2, PI180=Math.PI/180,
	systems=[];

/* PlanetarySystem */
	let PlanetarySystem = function(id='pSys'){
		Object.defineProperty(this, 'id',               { value:id, writable:true} );
		Object.defineProperty(this, 'x',                { value:0, writable:true });
		Object.defineProperty(this, 'y',                { value:0, writable:true });
		Object.defineProperty(this, 'allBodies',        { value:[], writable:true });
		Object.defineProperty(this, 'allBodiesLookup',  { value:{}, writable:true });    // fast id lookup for children
		Object.defineProperty(this, 'numBodies',        { value:0, writable:true });
	}
	PlanetarySystem.prototype.addBody = function(vo) {
		vo.parentSystem = this;
		vo.parentBody = vo.parentBody === null ? this : this.allBodiesLookup[vo.parentBody];
		let body = new PlanetaryBody(vo);
		body.update();
		this.allBodies.push(body);
		this.allBodiesLookup[vo.id] = body;
		this.numBodies += 1;
	}
	PlanetarySystem.prototype.setSpeedFactor = function(value){
		let body;
		for(let i=0; i<this.numBodies; i++){
			body = this.allBodies[i];
			body.setSpeedFactor(value);
		}
	}
	PlanetarySystem.prototype.update = function(){
		let body;
		for(let i=0; i<this.numBodies; i++){
			body = this.allBodies[i];
			body.update();
		}
	}
/* PlanetaryBody */
	let PlanetaryBody = function(vo){
		Object.defineProperty(this, 'id',					{ value:vo.id, writable:true} );
		Object.defineProperty(this, 'diameter',				{ value:vo.diameter, writable:true });
		Object.defineProperty(this, 'colour',				{ value:vo.colour, writable:true });
		Object.defineProperty(this, 'x',					{ value:0, writable:true });
		Object.defineProperty(this, 'y',					{ value:0, writable:true });
		Object.defineProperty(this, 'vx',					{ value:0, writable:true });
		Object.defineProperty(this, 'vy',					{ value:0, writable:true });
		Object.defineProperty(this, 'degrees',				{ value:vo.degrees, writable:true });
		Object.defineProperty(this, 'speedBase',			{ value:vo.speed, writable:true });
		Object.defineProperty(this, 'speed',				{ value:vo.speed , writable:true });
		Object.defineProperty(this, 'orbitalRadius',		{ value:vo.orbitalRadius, writable:true });
		Object.defineProperty(this, 'parentSystem',			{ value:vo.parentSystem, writable:true });
		Object.defineProperty(this, 'parentBody',			{ value:vo.parentBody, writable:true });

		return this;
	}
	PlanetaryBody.prototype.update = function(){
		let angle = this.degrees * PI180;
		this.degrees += this.speed;
		this.vx = this.orbitalRadius * Math.cos(angle);
		this.vy = this.orbitalRadius * Math.sin(angle);
		// update position
		if(this.parentBody != null){
			this.x = this.vx + this.parentBody.x;
			this.y = this.vy + this.parentBody.y;
		}
	}

/* init() */
	function init(){
		wrapper = document.querySelector('#wrapper');
		canvas = createCanvas('canvas', width, height);
		wrapper.appendChild(canvas);
		ctx = canvas.getContext('2d');
		setupEvents();
		resizeCanvas();

		/* Define new PlanetarySystem and set values */
		let system1 = new PlanetarySystem('pSys1');
		systems.push(system1);
		system1.x = width * .5;
		system1.y = height * .5;
		system1.addBody({id:'sun', diameter:5, degrees:0, speed:0, colour:'#FDFE1D', orbitalRadius:0, parentBody:null});
		for(let loop=30, i=0; i<loop; i+=1){
			system1.addBody({	id:				'ball'+i,
								diameter:		5,
								degrees:		0,
								speed:			2 + (loop * 0.15) - (i* 0.2),
								colour:			'#FDFE1D',
								orbitalRadius:	7*(i+1),
								parentBody:		'sun'});
		}
	}
	
/* Methods */
	function createCanvas(id, w, h){
		let tCanvas = document.createElement('canvas');
		tCanvas.width = w;
		tCanvas.height = h;
		tCanvas.id = id;
		return tCanvas;
	}

	function setupEvents(){
		window.onresize = resizeCanvas;
	}
	function resizeCanvas(){
		let rect = wrapper.getBoundingClientRect();
		width = window.innerWidth;
		height = window.innerHeight - rect.top -2;
		canvas.width = width;
		canvas.height = height;
		for(let i=0; i<systems.length; i++){
			systems[i].x = width * .5;
			systems[i].y = height * .5;
		}
	}

	function update(){
		for(let loop=systems.length, i=0; i<loop; i++){
			systems[i].update();
		}
	}

	function draw(){
		let system;
		let prev = null;
		for(let i=0; i<systems.length; i++){
			system = systems[i];
			let planetaryBody;
			for(let loop=system.numBodies, j=1; j<loop; j+=1) {
				planetaryBody = system.allBodies[j];
				ctx.beginPath();
				ctx.arc(planetaryBody.x, planetaryBody.y, planetaryBody.diameter, 0, Tau, false);
				ctx.fillStyle = planetaryBody.colour;
				ctx.fill();
				if(j>1){
					ctx.strokeStyle = planetaryBody.colour;
					ctx.lineWidth = 2;
					ctx.beginPath();
					ctx.moveTo(planetaryBody.x, planetaryBody.y);
					ctx.lineTo(prev.x, prev.y);
					ctx.stroke();
				}
				prev = {x:planetaryBody.x, y:planetaryBody.y};
			}
		}
	}

	function animate(){
		ctx.fillStyle = 'rgba(0,0,0, .05)';
		ctx.fillRect(0, 0, width, height);
		update();
		draw();
		requestAnimationFrame(animate);
	}
	init();
	animate();
}());
</script>
</html>

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