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JS+Canvas draws clock effect

高洛峰
高洛峰Original
2017-02-08 14:56:55909browse

The example in this article shares the specific code for drawing a clock using canvas for your reference. The specific content is as follows

1. clock.html 

<!doctype html>
<html>
 <head>
 <meta charset="UTF-8">
 <meta name="Description" content="">
 <title>canvas时钟</title>
 </head>
 <body>
  <canvas id="canvas" width="300" height="300"></canvas>
  <script>
    var canvas=document.getElementById("canvas");
    var context=canvas.getContext(&#39;2d&#39;);
    //draw();
    function draw(){
      //得到当前系统的时分秒
      var now=new Date();
      var sec=now.getSeconds();
      var min=now.getMinutes();
      var hour=now.getHours();
      hour>=12&&(hour=hour-12);
  
        
      var radius = Math.min(canvas.width/2,canvas.height/2);
      //初始化画布
      context.save();
      context.clearRect(0,0,canvas.width,canvas.height);
       context.translate(canvas.width/2,canvas.height/2); 
      context.rotate(-Math.PI/2);
      context.save();
    
      //表框
        
  
      //小时刻度
      context.strokeStyle="black";
      context.fillStyle="black";
      context.lineWidth=3;
      context.lineCap="round";
      context.beginPath();
      for(var i=0;i<12;i++){
        context.rotate(Math.PI/6);
        context.moveTo(radius-30,0);
        context.lineTo(radius-10,0);
  
      }
      context.stroke();
      context.restore();
      context.save();
  
      //分钟刻度
      context.lineWidth=2;
      context.beginPath();
      for(var i=0;i<60;i++){
        if(!i%5==0){
        context.moveTo(radius-15,0);
        context.lineTo(radius-10,0);
        }
        context.rotate(Math.PI/30);
      }
      context.stroke();
      context.restore();
      context.save();
  
      //画上时针
  
       context.rotate((Math.PI/6)*hour+(Math.PI/360)*min+(Math.PI/21600)*sec);
       context.lineWidth=6;
       context.beginPath();
       context.moveTo(-10,0);
       context.lineTo(radius*0.5,0);
       context.stroke();
      context.restore();
      context.save();
  
       context.rotate((Math.PI/30)*min+(Math.PI/1800)*sec);
   context.strokeStyle="#29A8DE";
   context.lineWidth=4;
   context.lineCap="butt";
   context.beginPath();
   context.moveTo(-20,0);
   context.lineTo(radius*0.7,0);
   context.stroke();
   context.restore();
   context.save();
  
   context.rotate(sec*Math.PI/30);
   context.strokeStyle="red";
   context.lineWidth=2;
   context.lineCap="butt";
   context.beginPath();
   context.moveTo(-30,0);
   context.lineTo(radius*0.9,0);
   context.stroke();
   context.restore();
   context.save();
  
      context.lineWidth=4;
       context.strokeStyle="gray";
      context.beginPath();
         context.arc(0,0,radius,0,Math.PI*2,true);
     context.stroke();
     context.restore();
  
  
     context.restore();
    }
  
    window.onload=function(){
      setInterval(draw,1000)
    }
  </script>
 </body>
</html>

2. JavaScript code

<script>
    var canvas=document.getElementById("canvas");
    var context=canvas.getContext(&#39;2d&#39;);
    //draw();
    function draw(){
      //得到当前系统的时分秒
      var now=new Date();
      var sec=now.getSeconds();
      var min=now.getMinutes();
      var hour=now.getHours();
      hour>=12&&(hour=hour-12);
  
        
      var radius = Math.min(canvas.width/2,canvas.height/2);
      //初始化画布
      context.save();
      context.clearRect(0,0,canvas.width,canvas.height);
       context.translate(canvas.width/2,canvas.height/2); 
      context.rotate(-Math.PI/2);
      context.save();
    
      //表框
        
  
      //小时刻度
      context.strokeStyle="black";
      context.fillStyle="black";
      context.lineWidth=3;
      context.lineCap="round";
      context.beginPath();
      for(var i=0;i<12;i++){
        context.rotate(Math.PI/6);
        context.moveTo(radius-30,0);
        context.lineTo(radius-10,0);
  
      }
      context.stroke();
      context.restore();
      context.save();
  
      //分钟刻度
      context.lineWidth=2;
      context.beginPath();
      for(var i=0;i<60;i++){
        if(!i%5==0){
        context.moveTo(radius-15,0);
        context.lineTo(radius-10,0);
        }
        context.rotate(Math.PI/30);
      }
      context.stroke();
      context.restore();
      context.save();
  
      //画上时针
  
       context.rotate((Math.PI/6)*hour+(Math.PI/360)*min+(Math.PI/21600)*sec);
       context.lineWidth=6;
       context.beginPath();
       context.moveTo(-10,0);
       context.lineTo(radius*0.5,0);
       context.stroke();
      context.restore();
      context.save();
  
       context.rotate((Math.PI/30)*min+(Math.PI/1800)*sec);
   context.strokeStyle="#29A8DE";
   context.lineWidth=4;
   context.lineCap="butt";
   context.beginPath();
   context.moveTo(-20,0);
   context.lineTo(radius*0.7,0);
   context.stroke();
   context.restore();
   context.save();
  
   context.rotate(sec*Math.PI/30);
   context.strokeStyle="red";
   context.lineWidth=2;
   context.lineCap="butt";
   context.beginPath();
   context.moveTo(-30,0);
   context.lineTo(radius*0.9,0);
   context.stroke();
   context.restore();
   context.save();
  
      context.lineWidth=4;
       context.strokeStyle="gray";
      context.beginPath();
         context.arc(0,0,radius,0,Math.PI*2,true);
     context.stroke();
     context.restore();
  
  
     context.restore();
    }
  
    window.onload=function(){
      setInterval(draw,1000)
    }
  </script>

The above is the entire content of this article. I hope it will be helpful to everyone in learning javascript programming.

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