<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>环状图</title>
<style>
body {
margin: 0;
padding: 50px 0;
background-color: #444;
}
ul,li {
list-style: none;
margin: 0;
padding: 0;
}
ul li {
float: left;
width: 33%;
text-align: center;
}
</style>
</head>
<body>
<div class="box">
<ul>
<li>
<canvas id="one" width="200" height="200"></canvas>
</li>
<li>
<canvas id="two" width="200" height="200"></canvas>
</li>
<li>
<canvas id="three" width="200" height="200"></canvas>
</li>
</ul>
</div>
</body>
<script>
function drawCircle(_options){
var options = _options || {}; //获取或定义options对象;
options.angle = options.angle || 1; //定义默认角度1为360度(角度范围 0-1);
options.color = options.color || '#fff'; //定义默认颜色（包括字体和边框颜色）;
options.lineWidth = options.lineWidth || 10; //定义默认圆描边的宽度;
options.lineCap = options.lineCap || 'square'; //定义描边的样式，默认为直角边，round 为圆角
var oBoxOne = document.getElementById(options.id);
var sCenter = oBoxOne.width / 2; //获取canvas元素的中心点;
var ctx = oBoxOne.getContext('2d');
var nBegin = Math.PI / 2; //定义起始角度;
var nEnd = Math.PI * 2; //定义结束角度;
var grd = ctx.createLinearGradient(0, 0, oBoxOne.width, 0); //grd定义为描边渐变样式;
grd.addColorStop(0, 'red');
grd.addColorStop(0.5, 'yellow');
grd.addColorStop(1, 'green');
ctx.textAlign = 'center'; //定义字体居中;
ctx.font = 'normal normal bold 20px Arial'; //定义字体加粗大小字体样式;
ctx.fillStyle = options.color == 'grd' ? grd : options.color; //判断文字填充样式为颜色，还是渐变色;
ctx.fillText((options.angle * 100) + '%', sCenter, sCenter); //设置填充文字;
/*ctx.strokeStyle = grd; //设置描边样式为渐变色;
ctx.strokeText((options.angle * 100) + '%', sCenter, sCenter); //设置描边文字(即镂空文字);*/
ctx.lineCap = options.lineCap;
ctx.strokeStyle = options.color == 'grd' ? grd : options.color;
ctx.lineWidth = options.lineWidth;
ctx.beginPath(); //设置起始路径，这段绘制360度背景;
ctx.strokeStyle = '#D8D8D8';
ctx.arc(sCenter, sCenter, (sCenter - options.lineWidth), -nBegin, nEnd, false);
ctx.stroke();
var imd = ctx.getImageData(0, 0, 240, 240);
function draw(current) { //该函数实现角度绘制;
ctx.putImageData(imd, 0, 0);
ctx.beginPath();
ctx.strokeStyle = options.color == 'grd' ? grd : options.color;
ctx.arc(sCenter, sCenter, (sCenter - options.lineWidth), -nBegin, (nEnd * current) - nBegin, false);
ctx.stroke();
}
var t = 0;
var timer = null;
function loadCanvas(angle) { //该函数循环绘制指定角度，实现加载动画;
timer = setInterval(function(){
if (t > angle) {
draw(options.angle);
clearInterval(timer);
}else{
draw(t);
t += 0.02;
}
}, 20);
}
loadCanvas(options.angle); //载入百度比角度 0-1 范围;
timer = null;
}
drawCircle({
id: 'one',
color: '#0000ff',
angle: 0.5,
lineWidth: 5
});
drawCircle({
id: 'two',
angle: 0.75,
color: '#ff0000',
lineWidth: 12
});
drawCircle({
id: 'three',
angle: 1,
lineWidth: 15,
color: 'grd'
});
</script>
</html>
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