HTML5 Canvas黑夜雪花飘落特效

	composer @Ta
	2015-07-20 21:28

---

一款HTML5 Canvas雪花特效，运行网页后可看到动态效果的雪花飘飘落下，随机位置，随机数量，速度可调节。

<canvas id="mc" width="420" height="280" style="border:1px solid black"></canvas>
<script type="text/javascript">
function createFlower(context,n,dx,dy,size,length){
 context.beginPath();
 context.moveTo(dx,dy+size);
 var dig = 2*Math.PI/n;
 for(var i=1;i<n+1;i++){
  var ctrlX = Math.sin((i-0.5)*dig)*length+dx;
  var ctrlY = Math.cos((i-0.5)*dig)*length+dy;
  var x = Math.sin(i*dig)*size+dx;
  var y = Math.cos(i*dig)*size+dy;
  context.quadraticCurveTo(ctrlX,ctrlY,x,y);
 }
 context.closePath();
}
snowPos = [
,,
,,
,,
,,
,,
,,
,];
function fall(context){
 context.fillStyle = "#000";
 context.fillRect(0,0,420,280);
 context.fillStyle = "#fff";
 for(var i=0,len=snowPos.length;i<len;i++){
  context.save();
  context.translate(snowPos<i>.x,snowPos<i>.y);
  context.rotate((Math.random()*6-3)*Math.PI/10);
  snowPos<i>.y += Math.random()*18;
  if(snowPos<i>.y>280){
   snowPos<i>.y=4;
  }
  createFlower(context,6,0,0,snowPos<i>.z,8);
  context.fill();
  context.restore();
 }
}
var canvas = document.getElementById("mc");
var ctx = canvas.getContext("2d");
setInterval("fall(ctx);",200);
</script>
 

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发表于2015-07-20 21:28

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