Duang~ Banner 特效 By Canvas

昨天晚上心血来潮,整了一下blog的模板,目前使用的是 BootCDN 1.0 ,根据自己的需求,修改了一些css,去除了一些暂时用不到的功能。

之前 banner 的背景是白色的,整站比较单调,就想整个背景上去,博主前端水平比较爪机,于是乎去找了一些资源,发现用有大婶用 canvas 模拟出了知乎的登录背景于是copy之。

最终用 canvas 做背景特效的代码( header.php 文件,部分代码根据自己的需求进行微调 ):

    <canvas id="Mycanvas" style="display: none;"></canvas>
    <header class="main-header" id="banner">
    <div class="container">
        <div class="row">
            <div class="col-sm-12">
                <h1><?php echo $blogname; ?></h1>
            </div>
        </div>
    </div>
    </header>
    <script>
        //定义画布宽高和生成点的个数
        var WIDTH = window.innerWidth,
            HEIGHT = 300,
//            HEIGHT = window.innerHeight,
            POINT = 35;

        var canvas = document.getElementById('Mycanvas');
        canvas.width = WIDTH,
            canvas.height = HEIGHT;
        var context = canvas.getContext('2d');
        context.strokeStyle = 'rgba(0,0,0,0.2)',
            context.strokeWidth = 1,
            context.fillStyle = 'rgba(0,0,0,0.1)';
        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();
                document.getElementById('banner').style.backgroundImage = 'url("' + context.canvas.toDataURL() + '")';
            }, 16);
        }
    </script>

get了别人的资源必须贴链接:

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