Canvas背景动画(五) 粒子星空-银河
效果动画展示：
直接上代码：
<!doctype html><html><head><meta charset="utf-8"><title>Canvas背景动画(五) 粒子星空-银河</title><style>body {background: #060e1b;overflow: hidden;}</style></head><body><canvas id="canvasBox"></canvas><script>"use strict";var canvas = document.getElementById('canvasBox'),ctx = canvas.getContext('2d'),w = canvas.width = window.innerWidth,h = canvas.height = window.innerHeight,hue = 217,stars = [],count = 0,maxStars = 1400;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, '#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) / 900000;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();</script></body></html>
