const staticImg = "https://img.swordpal.cn/imgs/qing.png";
const weatherImg = "https://img.swordpal.cn/imgs/spring.png";
const img = new Image();
img.src = weatherImg;
img.onload = function () {
    startSakura();
}


staticWeather();


var stop;

function Sakura(x, y, s, r, fn) {
    this.x = x;
    this.y = y;
    this.s = s;
    this.r = r;
    this.fn = fn;
}

Sakura.prototype.draw = function (cxt) {
    cxt.save();
    const img = new Image();
    img.src = weatherImg;
    cxt.translate(this.x, this.y);
    cxt.rotate(this.r);
    cxt.drawImage(img, 0, 0, 20 * this.s, 20 * this.s)
    cxt.restore();
}

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);
    if (this.x > window.innerWidth ||
        this.x < 0 ||
        this.y > window.innerHeight ||
        this.y < 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');
        }
    }
}

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

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;
}

function startSakura() {

    requestAnimationFrame = window.requestAnimationFrame ||
        window.mozRequestAnimationFrame ||
        window.webkitRequestAnimationFrame ||
        window.msRequestAnimationFrame ||
        window.oRequestAnimationFrame;
    var canvas = document.createElement('canvas'),
        cxt;
    canvas.height = document.getElementById('page-header').offsetHeight;
    canvas.width = window.innerWidth;
    canvas.setAttribute('style', 'position: absolute;left: 0;top: 0;pointer-events: none;z-index: 99;');
    canvas.setAttribute('id', 'canvas_sakura');
    document.getElementsByTagName('body')[0].appendChild(canvas);
    cxt = canvas.getContext('2d');
    var sakuraList = new SakuraList();
    for (var i = 0; i < 50; 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
        });
        sakura.draw(cxt);
        sakuraList.push(sakura);
    }
    stop = requestAnimationFrame(function () {
        cxt.clearRect(0, 0, canvas.width, canvas.height);
        sakuraList.update();
        sakuraList.draw(cxt);
        stop = requestAnimationFrame(arguments.callee);
    })
}


function staticWeather() {
    const canvas = document.createElement('canvas');
    let height = document.getElementById('page-header').offsetHeight;
    let width = window.innerWidth;
    canvas.height = height;
    canvas.width = width;
    canvas.setAttribute('style', 'position: absolute;left: 0;top:0;pointer-events: none;z-index: 99;');
    canvas.setAttribute('id', 'sun');
    document.getElementsByTagName('body')[0].appendChild(canvas);
    const c = document.getElementById("sun");
    const ctx = c.getContext("2d");

    const img = new Image();
    img.src = staticImg;

    img.onload = function () {
        ctx.drawImage(img, width / 2, height / 7)
    }
}



<canvas height="360" width="725" style="position: absolute;left: 0;top: 0;pointer-events: none;z-index: 99;" id="canvas_sakura"></canvas>