CANVAS 水波动态背景

时间：2022-09-13 14:40:50

参考：https://github.com/cyclegtx/wave_background

做的水波背景，以后可能会用到哈！

效果如下：

CANVAS 水波动态背景

代码如下：

<!DOCTYPE html>

<html>

<head>

    <title>水波背景</title>

    <meta charset="utf-8" />

    <style>

    html, body {width:100%; height:100%; padding:0; margin:0;}

    </style>

</head>

<body>

    <canvas id="canvas" style="position:absolute;top:0px;left:0px;z-index:1;"></canvas>

    <script type="text/javascript">

        var canvas = document.getElementById('canvas');

        var ctx = canvas.getContext('2d');

        canvas.width = canvas.parentNode.offsetWidth;

        canvas.height = canvas.parentNode.offsetHeight;

        //如果浏览器支持requestAnimFrame则使用requestAnimFrame否则使用setTimeout

        window.requestAnimFrame = (function(){

        return  window.requestAnimationFrame       ||

                window.webkitRequestAnimationFrame ||

                window.mozRequestAnimationFrame    ||

                function( callback ){

                  window.setTimeout(callback, 1000 / 60);

                };

        })();

        // 波浪大小

        var boHeight = canvas.height / 10;

        var posHeight = canvas.height / 1.2;

        //初始角度为0

        var step = 0;

        //定义三条不同波浪的颜色

        var lines = ["rgba(0,222,255, 0.2)",

                       "rgba(157,192,249, 0.2)",

                       "rgba(0,168,255, 0.2)"];

        function loop(){

            ctx.clearRect(0,0,canvas.width,canvas.height);

            step++;

            //画3个不同颜色的矩形

            for(var j = lines.length - 1; j >= 0; j--) {

                ctx.fillStyle = lines[j];

                //每个矩形的角度都不同，每个之间相差45度

                var angle = (step+j*50)*Math.PI/180;

                var deltaHeight   = Math.sin(angle) * boHeight;

                var deltaHeightRight   = Math.cos(angle) * boHeight;

                ctx.beginPath();

                ctx.moveTo(0, posHeight+deltaHeight);

                ctx.bezierCurveTo(canvas.width/2, posHeight+deltaHeight-boHeight, canvas.width / 2, posHeight+deltaHeightRight-boHeight, canvas.width, posHeight+deltaHeightRight);

                ctx.lineTo(canvas.width, canvas.height);

                ctx.lineTo(0, canvas.height);

                ctx.lineTo(0, posHeight+deltaHeight);

                ctx.closePath();

                ctx.fill();

            }

            requestAnimFrame(loop);

        }

        loop();

    </script>

</body>

</html>

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