canvas+js画饼状图

时间：2023-12-31 21:49:08

效果：

canvas+js画饼状图

源码：

<!DOCTYPE html>

<html lang="en">

<head>

    <meta charset="UTF-8">

    <title>饼状图</title>

</head>

<body>

<canvas id="canvas"></canvas>

<script>

    (function () {

        var data = [{

            "value":"0.4",

            "color":"red",

            "name":"JAVA"

        },{

            "value":"0.3",

            "color":"green",

            "name":"PYTHON"

        },{

            "value":"0.2",

            "color":"blue",

            "name":"C++"

        },{

            "value":"0.1",

            "color":"grey",

            "name":"PHP"

        }];

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

       //设置宽高不从css中设置

       canvas.width = 600;//设置canvas宽

       canvas.height = 600;//设置canvas高

       canvas.style.border = "1px solid red";

        //获取上下文

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

       //画图

        var x0  = 300,y0 = 300;//圆心

        var x,y;//文字放置位置

        var radius = 100;

        var tempAngle = -90;//画圆的起始角度

        for(var i = 0;i<data.length;i++){

            var startAngle = tempAngle*Math.PI/180;//起始弧度

            var angle = data[i].value*360;

            var endAngle = (tempAngle+angle)*Math.PI/180;//结束弧度

            var textAngle = tempAngle + 0.5*angle;//文字放的角度

            x = x0 + Math.cos(textAngle*Math.PI/180)*(radius+20);//文字放的X轴

            y = y0 + Math.sin(textAngle*Math.PI/180)*(radius+20);//文字放的Y轴

            //如果文字在圆形的左侧，那么让文字 对齐方式为 文字结尾对齐当前坐标。

            if( textAngle > 90 && textAngle < 270 ) {

                ctx.textAlign = 'end';

            }

            var text = data[i].name + " "+ data[i].value*100+"%";

            ctx.fillText(text,x,y);

            ctx.beginPath();

            ctx.moveTo(x0,y0);

            ctx.fillStyle = data[i].color;

            ctx.arc(x0,y0,radius,startAngle,endAngle);

            ctx.fill();

            tempAngle += angle;

        }

    }());

</script>

</body>

</html>

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