使用canvas元素绘制指针式动画时钟

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<!DOCTYPE html>   <head>   <meta charset="UTF-8">  <title>使用canvas元素绘制指针式动画时钟</title>  <script type="text/javascript">var canvas;var context;//页面装载function window_onload(){    canvas=document.getElementById("canvas");//获取canvas元素    context=canvas.getContext('2d');//获取canvas元素的图形上下文对象    setInterval("draw()",1000);//每隔一秒重绘时钟，重新显示时间}//绘制时钟function draw(){        var radius=Math.min(canvas.width / 2, canvas.height / 2) -25;//时钟罗盘半径    var centerx=canvas.width/2;//时钟中心横坐标    var centery=canvas.height/2;//时钟中心纵坐标    context.clearRect(0,0,canvas.width,canvas.height);//擦除之前所绘时钟    context.save();//保存当前绘制状态       //绘制时钟圆盘    context.fillStyle = '#efefef';//时钟背景色    context.strokeStyle = '#c0c0c0';//时钟边框颜色    context.beginPath();//开始创建路径    context.arc(centerx,centery,radius, 0,Math.PI*2, 0);//创建圆形罗盘路径    context.fill();//用背景色填充罗盘    context.stroke();//用边框颜色绘制罗盘边框    context.closePath();//关闭路径    context.restore();//恢复之前保存的绘制状态        //绘制时钟上表示小时的文字    var r = radius - 10;//缩小半径，因为要将文字绘制在时钟内部    context.font= 'bold 16px 宋体';//指定文字字体    Drawtext('1', centerx + (0.5 * r), centery - (0.88 * r));    Drawtext('2', centerx + (0.866 * r), centery - (0.5 * r));    Drawtext('3', centerx + radius - 10,centery);    Drawtext('4', centerx + (0.866 * r), centery + (0.5 * r));    Drawtext('5', centerx + (0.5 * r), centery + (0.866 * r));    Drawtext('6', centerx, centery + r);    Drawtext('7', centerx - (0.5 * r), centery + (0.866 * r));    Drawtext('8', centerx - (0.866 * r), centery + (0.49 * r));    Drawtext('9', centerx - radius + 10, centery);    Drawtext('10',centerx - (0.866 * r),centery - (0.50 * r));    Drawtext('11', centerx - (0.51 * r), centery - (0.88 * r));    Drawtext('12', centerx, 35);    //绘制时钟指针        var date=new Date();//获取需要表示的时间    var h = date.getHours();//获取当前小时    var m = date.getMinutes();//获取当前分钟    var s=date.getSeconds();//获取当前秒    var a = ((h/12) *Math.PI*2) - 1.57 + ((m / 60) * 0.524);//根据当前时间计算指针角度            context.save();//保存当前绘制状态          context.fillStyle='black'; //指定指针中心点的颜色    context.beginPath();//开始创建路径    context.arc(centerx,centery,3,0,Math.PI * 2, 0);//创建指针中心点的路径    context.closePath();//关闭路径    context.fill();//填充指针中心点    context.lineWidth=3;//指定指针宽度       context.fillStyle='darkgray';//指定指针填充颜色    context.strokeStyle='darkgray';//指定指针边框颜色    context.beginPath();//开始创建路径    //绘制小时指针    context.arc(centerx,centery,radius - 55, a + 0.01, a, 1);    context.lineTo(centerx,centery);    //绘制分钟指针    context.arc(centerx,centery,radius - 40, ((m/60) * 6.27) - 1.57, ((m/60) * 6.28) - 1.57, 0);    context.lineTo(canvas.width / 2, canvas.height / 2);    //绘制秒钟指针    context.arc(centerx,centery,radius - 30, ((s/60) * 6.27) - 1.57, ((s/60) * 6.28) - 1.57, 0);    context.lineTo(centerx,centery);    context.closePath();//关闭路径    context.fill();//填充指针    context.stroke();//绘制指针边框    context.restore();//恢复之前保存的绘制状态        //指定时钟下部当前时间所用的字符串，文字格式为hh:mm:dd    var hours   = String(h);    var minutes = String(m);    var seconds = String(s);    if (hours.length == 1)   h   = '0' + h;    if (minutes.length == 1) m = '0' + m;    if (seconds.length == 1) s = '0' + s;    var str =h + ':' + m + ':' +s;    //绘制时钟下部的当前时间    Drawtext(str, centerx, centery + radius + 12);}function Drawtext(text, x, y){    //因为需要使用到坐标平移，所以在平移前线保存当前绘制状态    context.save();    x -= (context.measureText(text).width / 2);//文字起点横坐标    y +=9;//文字起点纵坐标    context.beginPath();//开始创建路径    context.translate(x, y);//平移坐标    context.fillText(text,0,0);//填充文字     context.restore();}</script> <style>div{        display: -moz-box;        display: -webkit-box;        -moz-box-pack: center;        -webkit-box-pack: center; width:100%;}canvas{    background-color:white;}</style> </head>  <body onload="window_onload()">  <div><h1>使用canvas元素绘制指针式动画时钟</h1></div><div><canvas id="canvas" width="200px" height="200px"></canvas></div>   //这里就是你的时钟的位置。</body>  </html>
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