1. 程式人生 > >旋轉的銀河---動態網頁背景

旋轉的銀河---動態網頁背景

旋轉的銀河程式碼

html程式碼:

<canvas id="canvas"></canvas>

css程式碼:

body {
  background: #060e1b;
  overflow: hidden;
}

canvas {
  //opacity: 0.5;
}

js程式碼:

"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; // Thanks @jackrugile for the performance tip! http://codepen.io/jackrugile/pen/BjBGoM // Cache gradient 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 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; } 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();