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Special effects - starry cosmic background effects

2022-07-24 06:41:00 【Jie_ one thousand nine hundred and ninety-seven】

Starry universe background effect

One . design sketch
Two . Implementation code

One . design sketch

Insert picture description here

Two . Implementation code

<!DOCTYPE html>
<html>

<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title> Starry universe background effect </title>
    <style> * {
       margin: 0; padding: 0; width: 100%; height: 100%; } .canvasContainer {
       width: 100%; height: 100%; overflow: hidden; } </style>
</head>

<body>
    <div class="canvasContainer">
        <canvas id="canvas"></canvas>
    </div>
    <script> // Cosmic effects  "use strict"; var canvas = document.getElementById('canvas'), ctx = canvas.getContext('2d'), w = canvas.width = window.innerWidth, h = canvas.height = window.innerHeight, hue = 217, stars = [], count = 0, maxStars = 2500;// The number of stars  var canvas2 = document.createElement('canvas'), ctx2 = canvas2.getContext('2d'); canvas2.width = 100; canvas2.height = 100; var half = canvas2.width / 2, 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) {
       var hold = max; max = min; min = hold; } return Math.floor(Math.random() * (max - min + 1)) + min; } function maxOrbit(x, y) {
       var max = Math.max(x, y), diameter = Math.round(Math.sqrt(max * max + max * max)); return diameter / 2; // The moving range of stars , The larger the value, the smaller the range , } var Star = function () {
       this.orbitRadius = random(maxOrbit(w, h)); this.radius = random(60, this.orbitRadius) / 18; // Star size  this.orbitX = w / 2; this.orbitY = h / 2; this.timePassed = random(0, maxStars); this.speed = random(this.orbitRadius) / 500000; // The speed at which the stars move  this.alpha = random(2, 10) / 10; count++; stars[count] = this; } Star.prototype.draw = function () {
       var x = Math.sin(this.timePassed) * this.orbitRadius + this.orbitX, y = Math.cos(this.timePassed) * this.orbitRadius + this.orbitY, 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 (var i = 0; i < maxStars; i++) {
       new Star(); } function animation() {
       ctx.globalCompositeOperation = 'source-over'; ctx.globalAlpha = 0.5; // tail  ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 2)'; ctx.fillRect(0, 0, w, h) ctx.globalCompositeOperation = 'lighter'; for (var i = 1, l = stars.length; i < l; i++) {
       stars[i].draw(); }; window.requestAnimationFrame(animation); } animation(); </script>

</body>

</html>