超酷！！HTML5 Canvas 水流样式 Loading 动画

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相关问答

Q1: 代码实现

HTML代码

接下来我们讲讲实现这个加载动画的大致思路和实现过程。

首先在页面上定义一个canvas元素，用来承载这个Loading动画的画布。

<canvas id='canvas'></canvas>

接下拉需要定义一个SVG滤镜，这个滤镜用来渲染Loading圈圈粒子化的效果。

<svg xmlns="http://www.w3.org/2000/svg" version="1.1">
    <defs>
        <filter id="shadowed-goo">
             <feGaussianBlur in="SourceGraphic" result="blur" stdDeviation="10" />
             <feColorMatrix in="blur" mode="matrix" values="1 0 0 0 0  0 1 0 0 0  0 0 1 0 0  0 0 0 18 -7" result="goo" />
             <feGaussianBlur in="goo" stdDeviation="3" result="shadow" />
             <feColorMatrix in="shadow" mode="matrix" values="0 0 0 0 0  0 0 0 0 0  0 0 0 0 0  0 0 0 1 -0.2" result="shadow" />
             <feOffset in="shadow" dx="1" dy="1" result="shadow" />
             <feBlend in2="shadow" in="goo" result="goo" />
             <feBlend in2="goo" in="SourceGraphic" result="mix" />
        </filter>
        <filter id="goo">
             <feGaussianBlur in="SourceGraphic" result="blur" stdDeviation="10" />
             <feColorMatrix in="blur" mode="matrix" values="1 0 0 0 0  0 1 0 0 0  0 0 1 0 0  0 0 0 18 -7" result="goo" />
             <feBlend in2="goo" in="SourceGraphic" result="mix" />
        </filter>
    </defs>
</svg>

CSS代码

这里我们先不谈页面中其他元素的样式，我们的重点是为canvas元素指定相应的svg滤镜：

#canvas {
	margin: 0px auto;
	display: block;
	filter: url("#shadowed-goo");
}

JavaScript代码

然后用JavaScript代码实现Loading加载动画。这里用到了canvas的2d动画绘制对象：

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");

getContext()方法可返回一个对象，该对象提供了用于在画布上绘图的方法和属性。

这个动画的核心是动态画一段弧线，代码如下：

ctx.fillStyle = "rgba(255,255,255," + this.al + ")";
ctx.beginPath();
ctx.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
ctx.fill();

下面是完整的JS代码：

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var p = [];
var particle = [];
var angle = Math.PI/4;
canvas.width = 600;
canvas.height = 600;
var width = canvas.width;
var height = canvas.height;

function getRandomInt(min, max) {
	return min + Math.floor(Math.random() * (max - min + 1));
}

function retinaReady() {
	var pixelRatio = window.devicePixelRatio || 1;
	var backingStore = ctx.webkitBackingStorePixelRatio || 1;
	window.ratio = pixelRatio / backingStore; // public var
	if (pixelRatio !== backingStore) {
		var oldWidth = canvas.width;
		var oldHeight = canvas.height;
		canvas.width = oldWidth * ratio;
		canvas.height = oldHeight * ratio;
		canvas.style.width = oldWidth + "px";
		canvas.style.height = oldHeight + "px";
		ctx.scale(window.ratio, window.ratio);
	}
}
retinaReady();
function run(a) {
	var r = 140;
	var x = r * Math.sin(a) + width / 2;
	var y = r * Math.cos(a) + ((height / 2)-80);
	var p;
	p = new Particle(x, y);
	particle.push(p);
}

function Particle(x, y) {
	this.x = x;
	this.y = y;
	this.r = getRandomInt(10, 16);
	this.v = {
		x: 0,
		y: 0
	};
	this.a = {
		x: 0,
		y: 0
	};
	this.al = 1;
}

Particle.prototype.update = function() {
	this.a.x = getRandomInt(-0.001, 0.001);
	this.a.y = getRandomInt(0.01, 0.02);
	this.v.x += this.a.x;
	this.v.y += this.a.y;
	this.x += this.v.x;
	this.y += this.v.y;

	if (this.r >= 0.01) {
		this.r -= 0.2;
		this.al -= 0.001;
	} else {
		this.r = 0;
		this.al = 0;
	}
};

Particle.prototype.draw = function() {
	ctx.fillStyle = "rgba(255,255,255," + this.al + ")";
	ctx.beginPath();
	ctx.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
	ctx.fill();
};

function animate() {
	ctx.clearRect(0, 0, width, height);
	run(angle);
	requestAnimationFrame(animate);
	for (var j = 0; j < particle.length; j++) {
		var p = particle[j];
		p.update();
		p.draw();
	}

	if (angle <= 2 * Math.PI) {
		angle += 0.04;
	} else {
		angle = 0;
	}
}
animate();

到这里为止，这个粒子流体状的Loading加载动画就完成了，文章最后也将源码献给大家。

Q2: 源码下载

完整的代码我已经整理出了一个源码包，供大家下载学习。