<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>Document</title>
<style type="text/css">
#c{
margin: 0 auto;
display: block;
}
#r{
display: block;
margin: 0 auto;
}
#r::before{
color: black;
content: attr(min);
padding-right: 10px;
}
#r::after{
color: black;
content: attr(max);
padding-left: 10px;
}
</style>
</head>
<body>
<canvas id="c"></canvas>
<input type="range" id="r" min="0" max="100" step="1" style="display:none">
<script type="text/javascript">
var canvas = document.getElementById('c');
var ctx = canvas.getContext('2d');
var range = document.getElementById('r');
// range.max='70'
//range控件信息
var rangeValue = range.value;
var nowRange = 0; //用于做一个临时的range
//画布属性
var mW = canvas.width = 250;
var mH = canvas.height = 250;
var lineWidth = 2;
//圆属性
var r = mH / 2; //圆心
var cR = r - 16 * lineWidth; //圆半径
//Sin 曲线属性
var sX = 0;
var sY = mH / 2;
var axisLength = mW; //轴长
var waveWidth = 0.015 ; //波浪宽度,数越小越宽
var waveHeight = 6; //波浪高度,数越大越高
var speed = 0.09; //波浪速度，数越大速度越快
var xOffset = 0; //波浪x偏移量
ctx.lineWidth = lineWidth;
//画圈函数
var IsdrawCircled = false;
var drawCircle = function(){
ctx.beginPath();
ctx.strokeStyle = '#1080d0';
ctx.arc(r, r, cR+5, 0, 2 * Math.PI);
ctx.stroke();
ctx.beginPath();
ctx.arc(r, r, cR, 0, 2 * Math.PI);
ctx.clip();
}
//画sin 曲线函数
var drawSin = function(xOffset){
ctx.save();
var points=[]; //用于存放绘制Sin曲线的点
ctx.beginPath();
//在整个轴长上取点
for(var x = sX; x < sX + axisLength; x += 20 / axisLength){
//此处坐标(x,y)的取点，依靠公式 “振幅高*sin(x*振幅宽 + 振幅偏移量)”
var y = -Math.sin((sX + x) * waveWidth + xOffset);
var dY = mH * (1 - nowRange / 100 );
points.push([x, dY + y * waveHeight]);
ctx.lineTo(x, dY + y * waveHeight);
}
//封闭路径
ctx.lineTo(axisLength, mH);
ctx.lineTo(sX, mH);
ctx.lineTo(points[0][0],points[0][1]);
ctx.fillStyle = '#1c86d1';
ctx.fill();
ctx.restore();
};
//写百分比文本函数
var drawText = function(){
ctx.save();
var size = 0.4*cR;
ctx.font = size + 'px Microsoft Yahei';
ctx.textAlign = 'center';
ctx.fillStyle = "rgba(06, 85, 128, 0.8)";
ctx.fillText(~~nowRange + '%', r, r + size / 2);
ctx.restore();
};
var render = function(){
ctx.clearRect(0, 0, mW, mH);
rangeValue = 30;
if(IsdrawCircled == false){
drawCircle();
}
if(nowRange <= rangeValue){
var tmp = 1;
nowRange += tmp;
}
if(nowRange > rangeValue){
var tmp = 1;
nowRange -= tmp;
}
drawSin(xOffset);
drawText();
xOffset += speed;
requestAnimationFrame(render);
}
render();
</script>
</body>
</html>
