canvas绘制简易百分比仪表盘dashboard

由于最近工作中，经常会遇到一些动态百分比的仪表盘，一开始都是用图片样式方式实现；
但是随着越来越多的项目，决定用canvas绘制一个简易的仪表盘，便于以后项目中直接使用；
现版本只是书写为方法形式，也许之后会有时间对其优化为插件形式。

简简单单而已，以下直接给出代码和执行过程中的三张截图：

<!doctype html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <meta http-equiv="Pragma" content="no-cache">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no"/>
    <meta name="format-detection" content="telephone=no"/>
    <meta name="apple-mobile-web-app-capable" content="yes"/>
    <meta name="apple-mobile-web-app-status-bar-style" content="black"/>
    <title>canvas绘制简易百分比仪表盘dashboard（建议最好用于移动端）</title>
    <style type="text/css">
        div{margin:1rem;background:#eee;padding:.3rem; position:relative }
        div canvas{background:#cacaca;
            -webkit-transform: rotateZ(-270deg);
            transform:rotateZ(-270deg);
            -webkit-animation:ani01 1s ease 0s both;
            animation:ani01 1s ease 0s both;
        }
 
        @-webkit-keyframes ani01 {
            0%{
                -webkit-transform:scale(.5,.5) rotateZ(-270deg);
                transform:scale(.5,.5) rotateZ(-270deg);
            }
            100%{
                -webkit-transform:scale(1,1) rotateZ(-90deg);
                transform:scale(1,1) rotateZ(-90deg);
            }
        }
        @keyframes ani01 {
            0%{
                -webkit-transform:scale(.5,.5) rotateZ(-270deg);
                transform:scale(.5,.5) rotateZ(-270deg);
            }
            100%{
                -webkit-transform:scale(1,1) rotateZ(-90deg);
                transform:scale(1,1) rotateZ(-90deg);
            }
        }
    </style>
</head>
<body>
 
<div>
    <canvas id="myCanvas1" data-percent="80">
        您的浏览器不支持canvas标签。
    </canvas>
    <span style="display:block;position:absolute;top:.94rem;left:.3rem;width:2rem;text-align:center;font-size:.5rem;font-family:microsoft Yahei" id="dushu" >0</span>
</div>
 
<script type="text/javascript" src="../js/flexible.js"></script>
<script type="text/javascript">
    var pper=0;
    var pper_interal;
    var dushu=document.getElementById('dushu');
 
    var aaa=drawCanvanPercent('myCanvas1','rem',2,'#0e9cfa',0.2,'#fff');
 
    function drawCanvanPercent(ele_id,dw,cir_r,cir_color,line_w,fill_color){
        if(dw=="rem"){
            cir_r=cir_r*(window.screen.width/10);
            line_w=line_w*(window.screen.width/10);
        }
        var canvas = document.getElementById(ele_id);
        var circle = {
            r : cir_r/2,      //圆的半径
            per : canvas.getAttribute('data-percent'),      //百分比分子
            color : cir_color,      //圆的颜色
            lineWidth : line_w      //圆的颜色
        };
        canvas.width=canvas.height=circle.r*2;
        canvas.style.borderRadius="50%";
        if(canvas.getContext){
            var ctx2 = canvas.getContext("2d");
            ctx2.fillStyle = fill_color;
            ctx2.arc(circle.r, circle.r, circle.r-circle.lineWidth/2, 0, Math.PI*2, false);
            ctx2.fill();
            var ctx = canvas.getContext("2d");
            pper_interal= setInterval(function () {
                drawMove(ctx,circle);
            }, 10);
        }
    }
 
    function drawMove(ctx,circle){
        if(pper>=circle.per){
            pper=circle.per;
            clearTimeout(pper_interal);
        }else{
            pper++;
        }
        dushu.innerText=pper+'%';
        ctx.beginPath();
        ctx.strokeStyle = circle.color;
        ctx.lineWidth=circle.lineWidth;
        ctx.arc(circle.r, circle.r, circle.r, 0, Math.PI*(pper/100)*360/180, false);
        ctx.stroke();
    }
    </script>
 
</body>
</html>