Vue 组件 - 登录页面的 Canvas 动画背景（旋转星空）

LoginBackground.vue

<template>
    <canvas id="canvas" width="100%" height="100%"></canvas>
</template>

<script>
    export default {
        name: "LoginBackground",
        methods: {
            canvas() {
                let _this = this;
                // 定义窗口大小变更通知事件
                window.onresize = function () {
                    // 窗口高度
                    _this.screenHeight = document.documentElement.clientHeight;
                };
                let canvas = document.getElementById('canvas');
                let ctx = canvas.getContext('2d');
                let w = canvas.width = window.innerWidth;
                let h = canvas.height = window.innerHeight;
                let hue = 217;
                let stars = [];
                let count = 0;
                let maxStars = 1300; // 星星数量

                let canvas2 = document.createElement('canvas');
                let ctx2 = canvas2.getContext('2d');
                canvas2.width = 100;
                canvas2.height = 100;
                let half = canvas2.width / 2;
                let gradient2 = ctx2.createRadialGradient(half, half, 0, half, half, half);
                gradient2.addColorStop(0.025, '#CCC');
                gradient2.addColorStop(0.1, 'hsl(' + hue + ', 61%, 33%)');
                gradient2.addColorStop(0.25, 'hsl(' + hue + ', 64%, 6%)');
                gradient2.addColorStop(1, 'transparent');

                ctx2.fillStyle = gradient2;
                ctx2.beginPath();
                ctx2.arc(half, half, half, 0, Math.PI * 2);
                ctx2.fill();

                // End cache

                function random(min, max) {
                    if (arguments.length < 2) {
                        max = min;
                        min = 0;
                    }

                    if (min > max) {
                        let hold = max;
                        max = min;
                        min = hold;
                    }

                    return Math.floor(Math.random() * (max - min + 1)) + min;
                }

                function maxOrbit(x, y) {
                    let max = Math.max(x, y);
                    let diameter = Math.round(Math.sqrt(max * max + max * max));
                    return diameter / 2;
                    // 星星移动范围，值越大范围越小，
                }

                let Star = function () {
                    this.orbitRadius = random(maxOrbit(w, h));
                    this.radius = random(60, this.orbitRadius) / 8;
                    // 星星大小
                    this.orbitX = w / 2;
                    this.orbitY = h / 2;
                    this.timePassed = random(0, maxStars);
                    this.speed = random(this.orbitRadius) / 50000;
                    // 星星移动速度
                    this.alpha = random(2, 10) / 10;

                    count++;
                    stars[count] = this;
                };

                Star.prototype.draw = function () {
                    let x = Math.sin(this.timePassed) * this.orbitRadius + this.orbitX;
                    let y = Math.cos(this.timePassed) * this.orbitRadius + this.orbitY;
                    let twinkle = random(10);

                    if (twinkle === 1 && this.alpha > 0) {
                        this.alpha -= 0.05;
                    } else if (twinkle === 2 && this.alpha < 1) {
                        this.alpha += 0.05;
                    }

                    ctx.globalAlpha = this.alpha;
                    ctx.drawImage(canvas2, x - this.radius / 2, y - this.radius / 2, this.radius, this.radius);
                    this.timePassed += this.speed;
                };

                for (let i = 0; i < maxStars; i++) {
                    /* eslint-disable no-new */
                    new Star();
                }

                function animation() {
                    ctx.globalCompositeOperation = 'source-over';
                    ctx.globalAlpha = 0.5; // 尾巴
                    ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 2)';
                    ctx.fillRect(0, 0, w, h);

                    ctx.globalCompositeOperation = 'lighter';
                    for (let i = 1, l = stars.length; i < l; i++) {
                        stars[i].draw();
                    }

                    window.requestAnimationFrame(animation);
                }

                animation();
            }
        },
        mounted() {
            this.canvas()
        }
    }
</script>

<style>
    #canvas {
        position: absolute;
        top: 0;
        right: 0;
        bottom: 0;
        left: 0;
        z-index: -1;
    }
</style>