旋转的星空特效代码

蓝叶    网站设计    2016-08-02    13399    0评论

html5特效代码旋转的星空，首先要设置背景为暗一点的背景色或者图片，例如设置成黑色的背景颜色，然后把代码复制到html文件里，设置下下方JS里的一些设置，如星星的数量、星星移动的范围、星星的大小等，保存后用支持html5的浏览器打开就能看到旋转的星空特效。

温馨提示：如果使用复制按钮代码出现错误，建议使用ctrl+c来复制代码。

body{background: black;padding: 0;margin: 0; overflow:hidden}

.header{margin: 0 auto;width: 100%;height: 100%;background-color: #000;position: relative;}

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 = 3000;//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();

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