HTML实现圣诞下雪效果的方法
直接创建一个HTML文件，复制进去下面的代码即可实现圣诞下雪效果：
>
<html>
<head>
<meta charset="utf-8"/>
<title>HTML实现圣诞下雪效果的方法title>
<style>
#snowContainer {
position: relative;
width: 100%;
height: 100vh;
background: url(snow.jpg);
background-size: cover;
}
#snowCanvas {
position: absolute;
top: 0;
left: 0;
}
style>
head>
<body>
<div id="snowContainer">div>
<script>
var canvas = document.createElement('canvas'),
ctx = canvas.getContext('2d'),
w = canvas.width = window.innerWidth,
h = canvas.height = window.innerHeight,
snowflakeCount = 400,
snowflakes = [];
function Snowflake() {
this.x = Math.random() * w;
this.y = Math.random() * h - h;
this.ttl = Math.random() * 100 + 100;
this.speed = Math.random() * 2;
this.velY = this.speed;
this.velX = 0;
this.size = 5;
this.alpha = 0.5 + Math.random() * 0.5;
}
Snowflake.prototype.update = function () {
this.y += this.velY;
this.x += this.velX;
if (this.y >= h) {
this.reset();
}
this.velX *= 0.98;
if (this.ttl < 0) {
this.reset();
}
this.ttl--;
};
Snowflake.prototype.reset = function () {
this.y = Math.random() * h - h;
this.x = Math.random() * w;
this.ttl = Math.random() * 100 + 100;
this.speed = Math.random() * 2;
this.velY = this.speed;
this.velX = 0;
this.size = 5;
this.alpha = 0.5 + Math.random() * 0.5;
};
function init() {
for (var i = 0; i < snowflakeCount; i++) {
snowflakes.push(new Snowflake());
}
loop();
}
function loop() {
requestAnimationFrame(loop);
ctx.clearRect(0, 0, w, h);
for (var i = 0; i < snowflakeCount; i++) {
var flake = snowflakes[i];
flake.update();
ctx.beginPath();
ctx.arc(flake.x, flake.y, flake.size, 0, Math.PI * 2);
ctx.fillStyle = 'rgba(255, 255, 255, ' + flake.alpha + ')';
ctx.fill();
}
}
canvas.setAttribute('id', 'snowCanvas');
document.getElementById('snowContainer').appendChild(canvas);
window.addEventListener('resize', function () {
w = canvas.width = window.innerWidth;
h = canvas.height = window.innerHeight;
});
init();
script>
body>
html>
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