<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no" />
<title>demo</title>
</head>
<body>
<style type="text/css">
.chart-box{display:inline-block;position:relative;}
.chart-box .angle{position:absolute;top:50%;left:50%;transform:translate(-50%,-50%);padding:8px;background-color:#6aaafa;color:#fff;}
.chart-box .angle p{margin:0;font-size:13px;font-weight:bold;}
</style>
<div class="chart-box">
<canvas id="canvas" width="400px" height="400px"></canvas>
<div class="angle">
<p class="angle1">270</p>
<p class="angle2">50</p>
</div>
</div>
<script>
function circleFn(angle1,angle2){
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var canvasW = canvas.clientWidth/2,
canvasH = canvas.clientHeight/2,
radius = canvasW - 50,
deg = Math.PI/180; //Math.PI/180为1度
for(var i=0; i<120; i++){
ctx.beginPath();
ctx.arc(canvasW,canvasH,radius,(i+1+i*2)*deg,(i+1+(i+1)*2)*deg,false);
ctx.lineWidth = 15;
ctx.strokeStyle = '#99b';
ctx.stroke();
ctx.closePath();
}
ctx.beginPath();//默认旋转中心点是(0,0)点，想要图形绕圆心旋转，要先把中心点移动到圆心
ctx.translate(canvasW,canvasH); //移动旋转中心点到圆心
ctx.rotate(angle1*deg); //按指定角度旋转形状
ctx.translate(-canvasW,-canvasH); //移动旋转中心点到(0,0)点
ctx.moveTo(canvasW,100);
ctx.lineTo(canvasW,canvasH*2-100);
ctx.fillStyle = '#b4ecdc';
ctx.stroke();
ctx.closePath();
ctx.beginPath();
ctx.translate(canvasW,canvasH); //移动旋转中心点到圆心
ctx.rotate(angle2*deg - angle1*deg); //当前形状的中心点受前一个形状的rotate形状，所以要用当前旋转角度-前一个形状的旋转角度
ctx.translate(-canvasW,-canvasH); //移动旋转中心点到(0,0)点
ctx.moveTo(canvasW,canvasH);
ctx.arc(canvasW,canvasH,radius-50,-95*deg,-85*deg);
ctx.fillStyle = '#63aeed';
ctx.fill();
ctx.closePath();
}
var angle1 = document.getElementsByClassName('angle1')[0].innerText,
angle2 = document.getElementsByClassName('angle2')[0].innerText;
circleFn(angle1,angle2);
</script>
</body>
</html>
网友评论