这是一款html5 canvas炫酷旋转银河系星空背景特效。该特效通过canvas来绘制银河系星盘，并制作星系旋转的效果，非常炫酷。
使用方法
HTML结构
该旋转银河系星空背景特效的HTML结果只需要一个<canvas>元素即可。
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<canvas id=”canvas”></canvas>
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JavaScript
然后通过下面的js代码来在canvas上绘制银河系，以及制作动画效果。
"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 = 1400;// Cache gradientvar 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, '#fff'); 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 cachefunction 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;}var Star = function() { this.orbitRadius = random(w / 2 - 50); this.radius = random(100, this.orbitRadius) / 10; this.orbitX = w / 2; this.orbitY = h / 2; this.timePassed = random(0, maxStars); this.speed = random(this.orbitRadius) / 100000; this.alpha = random(2, 10) / 10; count++; stars[count] = this;}Star.prototype.draw = function() { var x = Math.sin(this.timePassed + 1) * this.orbitRadius + this.orbitX, y = Math.cos(this.timePassed) * this.orbitRadius/2 + 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 = 0.8; ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 1)'; 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(); |
