html 星空效果,HTML5JSstar_动态星空效果

一、案例介绍

这个案例主要运用了html5播放引用的功能。

播放音乐代码如下：

星空效果是用canvas绘制的，代码如下：

"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 = 1300;//星星数量

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;

//星星移动范围，值越大范围越小，

}

var 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 () {

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; //尾巴 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();