给大家分享一个用Canvas绘图写成的动画特效，动画的效果如下：
以下是代码实现：
代码语言：javascript复制<!DOCTYPE html>
<html>
<head>
<title>Canvas特效动画</title>
<style>
canvas {
background: #eee;
}
</style>
<script>
window.onload = function () {
var canvas = document.getElementById("canvas");
var cobj = canvas.getContext("2d");
var starArr = [];
for (var i = 0; i < 30; i ) {
var starObj = {
radius1: 20 10 * Math.random(),
radius2: 8 7 * Math.random(),
x: 30 (canvas.width - 60) * Math.random(),
y: 30 (canvas.height - 60) * Math.random(),
num: Math.ceil(4 4 * Math.random()),
color: "rgb(" parseInt(255 * Math.random()) "," parseInt(255 * Math.random()) "," parseInt(255 * Math.random()) ")",
angle: 360 * Math.random(),
changeAngle: -5 10 * Math.random()
};
starArr.push(starObj);
}
setInterval(function () {
cobj.clearRect(0, 0, 500, 500);
for (var i = 0; i < starArr.length; i ) {
starArr[i].angle = starArr[i].changeAngle;
cobj.save();
cobj.beginPath();
cobj.translate(starArr[i].x, starArr[i].y);
cobj.rotate(starArr[i].angle * Math.PI / 180);
cobj.scale(Math.sin(starArr[i].angle * Math.PI / 180), Math.sin(starArr[i].angle * Math.PI / 180))
cobj.globalAlpha = Math.abs(Math.sin(starArr[i].angle * Math.PI / 180));
drawStar(0, 0, starArr[i].radius1, starArr[i].radius2, starArr[i].num, "fill", starArr[i].color);
cobj.restore();
}
}, 60);
function drawStar(x, y, radius1, radius2, num, drawType, color) {
var angle = 360 / (num * 2);
var arr = [];
for (var i = 0; i < num * 2; i ) {
var starObj = {};
if (i % 2 == 0) {
starObj.x = x radius1 * Math.cos(i * angle * Math.PI / 180);
starObj.y = y radius1 * Math.sin(i * angle * Math.PI / 180);
} else {
starObj.x = x radius2 * Math.cos(i * angle * Math.PI / 180);
starObj.y = y radius2 * Math.sin(i * angle * Math.PI / 180);
}
arr.push(starObj);
}
cobj.beginPath();
cobj.fillStyle = color;
cobj.strokeStyle = color;
cobj.moveTo(arr[0].x, arr[0].y);
for (var i = 1; i < arr.length; i ) {
cobj.lineTo(arr[i].x, arr[i].y);
}
cobj.closePath();
if (drawType == "fill") {
cobj.fill();
} else {
cobj.stroke();
}
}
}
</script>
</head>
<body>
<canvas id="canvas" width=500 height=500></canvas>
</body>
</html>
