canvas繪製圓形鐘錶程式碼例項

antzone發表於2018-05-11
Canvas

分享一段程式碼例項，它實現了使用canvas繪製圓形鐘錶的功能。

並且鐘錶能夠實時獲取本機時間自動更新走動。

程式碼例項如下:

[HTML] 純文字檢視 複製程式碼執行程式碼
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="author" content="http://www.softwhy.com/" />
<title>螞蟻部落</title>
<style type="text/css">
div{
  text-align:center;
  margin-top:250px;
}
</style>
<script type="text/javascript">
window.onload = function() {
  var c = document.getElementById("clock");
  var ctx = c.getContext('2d');
  var width = ctx.canvas.width;
  var height = ctx.canvas.width;
  var r = width / 2;
  var rem = width / 200;
 
  function drawBackground() {
    ctx.save();
    ctx.translate(r, r);
    ctx.beginPath();
    ctx.lineWidth = 10 * rem;
    ctx.arc(0, 0, r - ctx.lineWidth / 2, 0, 2 * Math.PI);
    ctx.stroke();
    var hourNumbers = [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2];
    ctx.font = 18 * rem + "px Arial";
    ctx.textAlign = "center";
    ctx.textBaseline = "middle";
    hourNumbers.forEach(function(number, i) {
      var rad = 2 * Math.PI / 12 * i;
      var x = Math.cos(rad) * (r - 30 * rem);
      var y = Math.sin(rad) * (r - 30 * rem);
      ctx.fillText(number, x, y);
    })
    for (var i = 0; i < 60; i++) {
      var rad = 2 * Math.PI / 60 * i;
      var x = Math.cos(rad) * (r - 15 * rem);
      var y = Math.sin(rad) * (r - 15 * rem);
      ctx.beginPath();
      if (i % 5 == 0) {
        ctx.fillStyle = '#000';
        ctx.arc(x, y, 2 * rem, 0, 2 * Math.PI)
      } else {
        ctx.fillStyle = '#ccc';
        ctx.arc(x, y, 2 * rem, 0, 2 * Math.PI)
      }
      ctx.fill();
    }
  }
 
  function drawHour(hour, minute) {
    ctx.save();
    ctx.beginPath();
    var rad = 2 * Math.PI / 12 * hour;
    var mrad = 2 * Math.PI / 12 / 60 * minute;
    ctx.rotate(rad + mrad);
    ctx.lineWidth = 6 * rem;
    ctx.lineCap = 'round';
    ctx.moveTo(0, 10 * rem);
    ctx.lineTo(0, -r / 2);
    ctx.stroke();
    ctx.restore()
  }
 
  function drawMinute(minute) {
    ctx.save();
    ctx.beginPath();
    var rad = 2 * Math.PI / 60 * minute;
    ctx.rotate(rad);
    ctx.lineWidth = 3 * rem;
    ctx.lineCap = 'round';
    ctx.moveTo(0, 10 * rem);
    ctx.lineTo(0, -r + 35 * rem);
    ctx.stroke();
    ctx.restore()
  }
 
  function drawSecond(second) {
    ctx.save();
    ctx.beginPath();
    ctx.fillStyle = '#c14543';
    var rad = 2 * Math.PI / 60 * second;
    ctx.rotate(rad);
    ctx.moveTo(-2 * rem, 20 * rem);
    ctx.lineTo(2 * rem, 20 * rem);
    ctx.lineTo(1, -r + 18 * rem);
    ctx.lineTo(-1, -r + 18 * rem);
    ctx.fill();
    ctx.restore()
  }
 
  function drawDot() {
    ctx.beginPath();
    ctx.fillStyle = '#fff';
    ctx.arc(0, 0, 3 * rem, 0, 2 * Math.PI);
    ctx.fill();
  }
 
  function draw() {
    ctx.clearRect(0, 0, width, height)
    var now = new Date();
    var hour = now.getHours();
    var minute = now.getMinutes();
    var second = now.getSeconds();
    drawBackground();
    drawHour(hour, minute);
    drawMinute(minute);
    drawSecond(second);
    drawDot();
    ctx.restore();
  }
  draw();
  setInterval(draw, 1000)
}               
</script>
</head>
<body>
<div>
  <canvas id="clock" width="300" height="300"></canvas>
</div>
</body>
</html>

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