canvas繪製網格射線效果

antzone發表於2018-07-08
Canvas

分享一段程式碼例項，它實現了利用canvas繪製網格射線的功能。

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>
body {
  background: #000;
  overflow: hidden;
  margin: 0;
  padding: 0;
}
canvas {
  width: 45%;
  margin: 5% 30%;
}
</style>
</head>
<body>
<canvas id="canv" width="600" height="600"></canvas>
<script type="text/javascript">
var c;
var $;
var w = 600;
var h = 600;
constant = 15;
var rad = 300;
var timeout = 0;
 
c = document.getElementById("canv");
$ = c.getContext("2d");
drawLines();
 
function drawLines() {
  $.fillRect(0, 0, w, h);
  $.translate(w / 2, h / 2);
  for (var i = 0; i < 25; i++) {
    for (var n = -45; n <= 45; n += constant) {
      setTimeout("draw(" + n + ");", 100 * timeout);
      timeout++;
    }
  }
}
 
function draw(n) {
  $.beginPath();
  $.moveTo(0, rad);
  var radians = Math.PI / 180 * n;
  var x = (rad * Math.sin(radians)) / Math.sin(Math.PI / 2 - radians);
  $.lineTo(x, 0);
 
  if (Math.abs(n) == 45) {
    $.strokeStyle = rndColor();
    $.lineWidth = 2;
  } else if (n == 0) {
    $.strokeStyle = "rgb(200,200,200)";
    $.lineWidth = .5;
  } else {
    $.strokeStyle = "rgb(110,110,110)";
    $.lineWidth = .5;
  }
  $.stroke();
  $.rotate((Math.PI / 180) * 15);
}
 
function rndColor() {
  var r = 255 * Math.random() | 0,
    g = 255 * Math.random() | 0,
    b = 255 * Math.random() | 0;
  return 'rgb(' + r + ',' + g + ',' + b + ')';
}
</script>
</body>
</html>

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