127 lines
4.7 KiB
JavaScript
127 lines
4.7 KiB
JavaScript
/* 控制下雪 */
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function snowFall(snow) {
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/* 可配置属性 */
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snow = snow || {};
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this.maxFlake = snow.maxFlake || 150; /* 最多片数 */
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this.flakeSize = snow.flakeSize || 10; /* 雪花形状 */
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this.fallSpeed = snow.fallSpeed || 1; /* 坠落速度 */
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}
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/* 兼容写法 */
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requestAnimationFrame = window.requestAnimationFrame ||
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window.mozRequestAnimationFrame ||
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window.webkitRequestAnimationFrame ||
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window.msRequestAnimationFrame ||
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window.oRequestAnimationFrame ||
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function(callback) { setTimeout(callback, 1000 / 60); };
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cancelAnimationFrame = window.cancelAnimationFrame ||
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window.mozCancelAnimationFrame ||
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window.webkitCancelAnimationFrame ||
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window.msCancelAnimationFrame ||
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window.oCancelAnimationFrame;
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/* 开始下雪 */
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snowFall.prototype.start = function(){
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/* 创建画布 */
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snowCanvas.apply(this);
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/* 创建雪花形状 */
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createFlakes.apply(this);
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/* 画雪 */
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drawSnow.apply(this)
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}
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/* 创建画布 */
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function snowCanvas() {
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/* 添加Dom结点 */
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var snowcanvas = document.createElement("canvas");
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snowcanvas.id = "snowfall";
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snowcanvas.width = document.body.offsetWidth;
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snowcanvas.height = window.innerHeight;
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snowcanvas.setAttribute("style", "position:fixed; top: 0; left: 0; z-index: 9999; pointer-events: none;");
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document.getElementsByTagName("body")[0].appendChild(snowcanvas);
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this.canvas = snowcanvas;
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this.ctx = snowcanvas.getContext("2d");
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/* 窗口大小改变的处理 */
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window.onresize = function() {
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// snowcanvas.width = document.body.offsetWidth;
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/* snowcanvas.height = window.innerHeight */
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}
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}
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/* 雪运动对象 */
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function flakeMove(canvasWidth, canvasHeight, flakeSize, fallSpeed) {
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this.x = Math.floor(Math.random() * canvasWidth); /* x坐标 */
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this.y = Math.floor(Math.random() * canvasHeight); /* y坐标 */
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this.size = Math.random() * flakeSize + 2; /* 形状 */
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this.maxSize = flakeSize; /* 最大形状 */
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this.speed = Math.random() * 1 + fallSpeed; /* 坠落速度 */
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this.fallSpeed = fallSpeed; /* 坠落速度 */
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this.velY = this.speed; /* Y方向速度 */
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this.velX = 0; /* X方向速度 */
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this.stepSize = Math.random() / 30; /* 步长 */
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this.step = 0 /* 步数 */
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}
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flakeMove.prototype.update = function() {
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var x = this.x,
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y = this.y;
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/* 左右摆动(余弦) */
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this.velX *= 0.98;
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if (this.velY <= this.speed) {
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this.velY = this.speed
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}
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this.velX += Math.cos(this.step += .05) * this.stepSize;
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this.y += this.velY;
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this.x += this.velX;
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/* 飞出边界的处理 */
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if (this.x >= canvas.width || this.x <= 0 || this.y >= canvas.height || this.y <= 0) {
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this.reset(canvas.width, canvas.height)
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}
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};
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/* 飞出边界-放置最顶端继续坠落 */
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flakeMove.prototype.reset = function(width, height) {
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this.x = Math.floor(Math.random() * width);
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this.y = 0;
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this.size = Math.random() * this.maxSize + 2;
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this.speed = Math.random() * 1 + this.fallSpeed;
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this.velY = this.speed;
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this.velX = 0;
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};
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// 渲染雪花-随机形状（此处可修改雪花颜色！！！）
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flakeMove.prototype.render = function(ctx) {
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var snowFlake = ctx.createRadialGradient(this.x, this.y, 0, this.x, this.y, this.size);
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snowFlake.addColorStop(0, "rgba(255, 255, 255, 0.9)"); /* 此处是雪花颜色，默认是白色 */
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snowFlake.addColorStop(.5, "rgba(255, 255, 255, 0.5)"); /* 若要改为其他颜色，请自行查 */
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snowFlake.addColorStop(1, "rgba(255, 255, 255, 0)"); /* 找16进制的RGB 颜色代码。 */
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ctx.save();
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ctx.fillStyle = snowFlake;
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ctx.beginPath();
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ctx.arc(this.x, this.y, this.size, 0, Math.PI * 2);
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ctx.fill();
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ctx.restore();
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};
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/* 创建雪花-定义形状 */
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function createFlakes() {
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var maxFlake = this.maxFlake,
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flakes = this.flakes = [],
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canvas = this.canvas;
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for (var i = 0; i < maxFlake; i++) {
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flakes.push(new flakeMove(canvas.width, canvas.height, this.flakeSize, this.fallSpeed))
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}
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}
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/* 画雪 */
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function drawSnow() {
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var maxFlake = this.maxFlake,
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flakes = this.flakes;
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ctx = this.ctx, canvas = this.canvas, that = this;
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/* 清空雪花 */
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ctx.clearRect(0, 0, canvas.width, canvas.height);
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for (var e = 0; e < maxFlake; e++) {
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flakes[e].update();
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flakes[e].render(ctx);
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}
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/* 一帧一帧的画 */
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this.loop = requestAnimationFrame(function() {
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drawSnow.apply(that);
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});
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}
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/* 调用及控制方法 */
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var snow = new snowFall({maxFlake:200});
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snow.start(); |