Canvas知乎登录页面背景动画js代码

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以下是 Canvas知乎登录页面背景动画js代码的示例演示效果:

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部分效果截图:

HTML代码(index.html):

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Canvas知乎登录页面背景动画</title>
<style type="text/css">
	body{
		text-align: center;
		background: #F7FAFC;
		overflow: hidden;
		background: #fff;
		}
</style>
</head>
<body>
<canvas id="Mycanvas"></canvas>
<script>
	//定义画布宽高和生成点的个数
	var WIDTH = window.innerWidth, HEIGHT = window.innerHeight, POINT = 35;
	
	var canvas = document.getElementById('Mycanvas');
	canvas.width = WIDTH,
	canvas.height = HEIGHT;
	var context = canvas.getContext('2d');
	context.strokeStyle = 'rgba(0,0,0,0.02)',
	context.strokeWidth = 1,
	context.fillStyle = 'rgba(0,0,0,0.05)';
	var circleArr = [];

	//线条：开始xy坐标，结束xy坐标，线条透明度
	function Line (x, y, _x, _y, o) {
		this.beginX = x,
		this.beginY = y,
		this.closeX = _x,
		this.closeY = _y,
		this.o = o;
	}
	//点：圆心xy坐标，半径，每帧移动xy的距离
	function Circle (x, y, r, moveX, moveY) {
		this.x = x,
		this.y = y,
		this.r = r,
		this.moveX = moveX,
		this.moveY = moveY;
	}
	//生成max和min之间的随机数
	function num (max, _min) {
		var min = arguments[1] || 0;
		return Math.floor(Math.random()*(max-min+1)+min);
	}
	// 绘制原点
	function drawCricle (cxt, x, y, r, moveX, moveY) {
		var circle = new Circle(x, y, r, moveX, moveY)
		cxt.beginPath()
		cxt.arc(circle.x, circle.y, circle.r, 0, 2*Math.PI)
		cxt.closePath()
		cxt.fill();
		return circle;
	}
	//绘制线条
	function drawLine (cxt, x, y, _x, _y, o) {
		var line = new Line(x, y, _x, _y, o)
		cxt.beginPath()
		cxt.strokeStyle = 'rgba(0,0,0,'+ o +')'
		cxt.moveTo(line.beginX, line.beginY)
		cxt.lineTo(line.closeX, line.closeY)
		cxt.closePath()
		cxt.stroke();

	}
	//初始化生成原点
	function init () {
		circleArr = [];
		for (var i = 0; i < POINT; i++) {
			circleArr.push(drawCricle(context, num(WIDTH), num(HEIGHT), num(15, 2), num(10, -10)/40, num(10, -10)/40));
		}
		draw();
	}

	//每帧绘制
	function draw () {
		context.clearRect(0,0,canvas.width, canvas.height);
		for (var i = 0; i < POINT; i++) {
			drawCricle(context, circleArr[i].x, circleArr[i].y, circleArr[i].r);
		}
		for (var i = 0; i < POINT; i++) {
			for (var j = 0; j < POINT; j++) {
				if (i + j < POINT) {
					var A = Math.abs(circleArr[i+j].x - circleArr[i].x),
						B = Math.abs(circleArr[i+j].y - circleArr[i].y);
					var lineLength = Math.sqrt(A*A + B*B);
					var C = 1/lineLength*7-0.009;
					var lineOpacity = C > 0.03 ? 0.03 : C;
					if (lineOpacity > 0) {
						drawLine(context, circleArr[i].x, circleArr[i].y, circleArr[i+j].x, circleArr[i+j].y, lineOpacity);
					}
				}
			}
		}
	}

	//调用执行
	window.onload = function () {
		init();
		setInterval(function () {
			for (var i = 0; i < POINT; i++) {
				var cir = circleArr[i];
				cir.x += cir.moveX;
				cir.y += cir.moveY;
				if (cir.x > WIDTH) cir.x = 0;
				else if (cir.x < 0) cir.x = WIDTH;
				if (cir.y > HEIGHT) cir.y = 0;
				else if (cir.y < 0) cir.y = HEIGHT;
				
			}
			draw();
		}, 16);
	}
</script>
</body>
</html>

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