樱花特效js

调用方法

<script src="https://files.cnblogs.com/files/quaint/sakuraPlus.js"></script>

解读

//樱花 Quaint 修改版

var stop, staticx;
var img = new Image();
img.src = "这里原js作者高明操作,请看源码,如何进制转成樱花";

// 樱花数量 (添加)
var sakuraNum = 21;
// 樱花越界限制次数, -1不做限制,无限循环 (添加)
var limitTimes = 2;

// 定义限制数组 (添加)
var limitArray = new Array(sakuraNum);
for(var index = 0;index < sakuraNum;index++){
    limitArray[index] = limitTimes;
}

// 定义樱花, idx 是修改添加的
function Sakura(x, y, s, r, fn, idx) {
    this.x = x;
    this.y = y;
    this.s = s;
    this.r = r;
    this.fn = fn;
    this.idx = idx;
}

// 绘制樱花
Sakura.prototype.draw = function(cxt) {
    cxt.save();
    var xc = 40 * this.s / 4;
    cxt.translate(this.x, this.y);
    cxt.rotate(this.r);
    cxt.drawImage(img, 0, 0, 40 * this.s, 40 * this.s)
    cxt.restore();
}

// 修改樱花位置,模拟飘落.
Sakura.prototype.update = function() {
    this.x = this.fn.x(this.x, this.y);
    this.y = this.fn.y(this.y, this.y);
    this.r = this.fn.r(this.r);

    // 如果樱花越界, 重新调整位置
    if(this.x > window.innerWidth || this.x < 0 ||
        this.y > window.innerHeight || this.y < 0) {

        // 如果樱花不做限制
        if (limitArray[this.idx] == -1) {
            this.r = getRandom('fnr');
            if(Math.random() > 0.4) {
                this.x = getRandom('x');
                this.y = 0;
                this.s = getRandom('s');
                this.r = getRandom('r');
            } else {
                this.x = window.innerWidth;
                this.y = getRandom('y');
                this.s = getRandom('s');
                this.r = getRandom('r');
            }
        }
        // 否则樱花有限制
        else {
            if (limitArray[this.idx] > 0) {
                this.r = getRandom('fnr');
                if(Math.random() > 0.4) {
                    this.x = getRandom('x');
                    this.y = 0;
                    this.s = getRandom('s');
                    this.r = getRandom('r');
                } else {
                    this.x = window.innerWidth;
                    this.y = getRandom('y');
                    this.s = getRandom('s');
                    this.r = getRandom('r');
                }
                // 该越界的樱花限制数减一
                limitArray[this.idx]--;
            }
        }
    }
}


SakuraList = function() {
    this.list = [];
}
SakuraList.prototype.push = function(sakura) {
    this.list.push(sakura);
}

// list update 方法
SakuraList.prototype.update = function() {
    for(var i = 0, len = this.list.length; i < len; i++) {
        this.list[i].update();
    }
}

// list draw 方法
SakuraList.prototype.draw = function(cxt) {
    for(var i = 0, len = this.list.length; i < len; i++) {
        this.list[i].draw(cxt);
    }
}
SakuraList.prototype.get = function(i) {
    return this.list[i];
}
SakuraList.prototype.size = function() {
    return this.list.length;
}

// 位置随机策略
function getRandom(option) {
    var ret, random;
    switch(option) {
        case 'x':
            ret = Math.random() * window.innerWidth;
            break;
        case 'y':
            ret = Math.random() * window.innerHeight;
            break;
        case 's':
            ret = Math.random();
            break;
        case 'r':
            ret = Math.random() * 6;
            break;
        case 'fnx':
            random = -0.5 + Math.random() * 1;
            ret = function(x, y) {
                return x + 0.5 * random - 1.7;
            };
            break;
        case 'fny':
            random = 1.5 + Math.random() * 0.7
            ret = function(x, y) {
                return y + random;
            };
            break;
        case 'fnr':
            random = Math.random() * 0.03;
            ret = function(r) {
                return r + random;
            };
            break;
    }
    return ret;
}

// 樱花入口
function startSakura() {
  
    requestAnimationFrame = window.requestAnimationFrame ||
        window.mozRequestAnimationFrame ||
        window.webkitRequestAnimationFrame ||
        window.msRequestAnimationFrame ||
        window.oRequestAnimationFrame;
    var canvas = document.createElement('canvas'),
        cxt;
    staticx = true;
    canvas.height = window.innerHeight;
    canvas.width = window.innerWidth;
    canvas.setAttribute('style', 'position: fixed;left: 0;top: 0;pointer-events: none;');
    canvas.setAttribute('id', 'canvas_sakura');
    document.getElementsByTagName('body')[0].appendChild(canvas);
    cxt = canvas.getContext('2d');
    var sakuraList = new SakuraList();
    // sakuraNum 樱花个数 (原版为50个)
    for(var i = 0; i < sakuraNum; i++) {
        var sakura, randomX, randomY, randomS, randomR, randomFnx, randomFny;
        randomX = getRandom('x');
        randomY = getRandom('y');
        randomR = getRandom('r');
        randomS = getRandom('s');
        randomFnx = getRandom('fnx');
        randomFny = getRandom('fny');
        randomFnR = getRandom('fnr');
        sakura = new Sakura(randomX, randomY, randomS, randomR, {
            x: randomFnx,
            y: randomFny,
            r: randomFnR
        }, i);
        sakura.draw(cxt);
        sakuraList.push(sakura);
    }

    stop = requestAnimationFrame(function() {
        cxt.clearRect(0, 0, canvas.width, canvas.height);
        // 修改樱花位置逻辑
        sakuraList.update();
        // 画出修改后的樱花
        sakuraList.draw(cxt);
        // 递归 修改位置, 画出修改后的樱花
        stop = requestAnimationFrame(arguments.callee);
    })
}

window.onresize = function() {
    var canvasSnow = document.getElementById('canvas_snow');
    // canvasSnow 在改变浏览器大小的时候会为null (修改空指针异常), 不过在改变大小时体验稍差
    if (canvasSnow) {
        canvasSnow.width = window.innerWidth;
        canvasSnow.height = window.innerHeight;
    }
}

img.onload = function() {
    startSakura();
}

// 没看懂哪里调用了, 应该是关闭樱花特效的方法. 还请大佬们解释自己是怎么使用的.
function stopp() {
    if(staticx) {
        var child = document.getElementById("canvas_sakura");
        child.parentNode.removeChild(child);
        window.cancelAnimationFrame(stop);
        staticx = false;
    } else {
        startSakura();
    }
}
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