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html5 canvas 倒计时

html5 canvas 倒计时

作者: Zoro_stack | 来源:发表于2016-06-09 13:13 被阅读0次
    <!DOCTYPE html>
    <html>
    <head>
      <title>Canvas</title>
    </head>
    
    <body>
      <canvas id="canvas" width="1000" height="1000"></canvas>
    
      <script type="text/javascript">
    
        var currentSeconds = 10;
        var countDownSeconds = 10;
    
        var interval_id = setInterval("drawDoubleCircle()", 1000);
    
        function drawDoubleCircle() {
          if (currentSeconds <= 0) {
            clearInterval(interval_id);
          }
          var canvasElement = document.getElementById('canvas');
          var context = canvasElement.getContext('2d');
          progress = 360 * currentSeconds / countDownSeconds;
          progress_pi = Math.PI * (progress / 180 - 1 / 2);
          context.beginPath();
          context.moveTo(700, 400);
          context.arc(700, 400, 80, 0, Math.PI * 2, false);
          context.closePath();
          context.fillStyle = '#4BF41B';
          context.fill();
    
          context.beginPath();
          context.moveTo(700, 400);
          context.arc(700, 400, 80, -Math.PI * 1 / 2, progress_pi, false);
          context.closePath();
          context.fillStyle = 'red'
          context.lineCap = 'round';
          context.fill();
    
          context.beginPath();
          context.arc(700, 400, 65, 0, Math.PI * 2, false);
          context.closePath();
          context.fillStyle = 'white';
          context.fill();
    
          context.font = "bold 40pt Arial";
          context.fillStyle = "red";
          context.textAlign = "center";
          context.textBaseline = 'middle';
          context.fillText(currentSeconds, 700, 400);
          // 抗锯齿
          context.globalCompositeOperation = 'source-atop';
          currentSeconds--;
        }
        </script>
    
    </body>
    </html>
    

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