知乎动态界面

有一天注册知乎，发现知乎的背景的动态图还是很漂亮的，然后就和朋友们探讨加上自己的研究手写了知乎的背景动态界面，显示出来的效果还不错，在以后的开发中可以做为一个组件进行使用，在生产代码的过程中有一个科技感十足的界面会显得得心应手。科技感十足。

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<canvas id="Mycanvas"></canvas>
</body>
<script>

    //定义画布宽高和生成点的个数
    var WIDTH = window.innerWidth, HEIGHT = window.innerHeight, POINT = 80;

    var canvas = document.getElementById('Mycanvas');
    canvas.width = WIDTH,
        canvas.height = HEIGHT;
    var context = canvas.getContext('2d');
    context.strokeStyle = 'rgba(0,0,0,1)',
        context.strokeWidth = 1,
        context.fillStyle = 'rgba(0,0,180,0.2)';
    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(10, 1), num(10, -10)/30, 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 ? 0.2 : 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();
        }, 2);
    };
</script>
</html>

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