canvas旋轉太極圖效果

admin發表於2018-01-27
Canvas
本章節分享一段程式碼例項，它實現了太極八卦圖的旋轉效果，感興趣的朋友可以做一下分析。

程式碼如下:

[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>  
</head>
<body> 
<canvas id="myCanvas" width="500" height="500" >瀏覽器不支援</canvas> 
<script type="text/javascript"> 
var canvas=document.getElementById('myCanvas'); 
var ctx = canvas.getContext("2d"); 
var angle = 0; 
var count = 360; 
var clrA = '#000'; 
var clrB = 'red';
function taiji(x, y, radius, angle, wise) { 
  angleangle = angle || 0; 
  wisewise = wise ? 1 : -1; 
  ctx.save(); 
  ctx.translate(x, y); 
  ctx.rotate(angle); 
  ctx.fillStyle = clrA; 
  ctx.beginPath(); 
  ctx.arc(0, 0, radius, 0, Math.PI, true); 
  ctx.fill(); 
  ctx.beginPath(); 
  ctx.fillStyle = clrB; 
  ctx.arc(0, 0, radius, 0, Math.PI, false); 
  ctx.fill(); 
  ctx.fillStyle = clrB; 
  ctx.beginPath(); 
  ctx.arc(wise * -0.5 * radius, 0, radius / 2, 0, Math.PI * 2, true); 
  ctx.fill(); 
  ctx.beginPath(); 
  ctx.fillStyle = clrA; 
  ctx.arc(wise * +0.5 * radius, 0, radius / 2, 0, Math.PI * 2, false); 
  ctx.arc(wise * -0.5 * radius, 0, radius / 10, 0, Math.PI * 2, true); 
  ctx.fill(); 
  ctx.beginPath(); 
  ctx.fillStyle = clrB; 
  ctx.arc(wise * +0.5 * radius, 0, radius / 10, 0, Math.PI * 2, true); 
  ctx.fill(); 
  ctx.restore(); 
} 
loop = setInterval(function () { 
  beginTag = true; 
  ctx.clearRect(0, 0, canvas.width, canvas.height); 
  taiji(200, 200, 50, Math.PI * (angle / count) * 2, true); 
  angle = (angle + 5) % count; 
}, 50); 
</script>
</body> 
</html>

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