http://blog.csdn.net/lecepin/article/details/53536445
<!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"> <script type="text/javascript"> var canvas = document.getElementById('c'); var ctx = canvas.getContext('2d'); var range = document.getElementById('r'); //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 = range.value; 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>