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JS+canvas畫布實(shí)現(xiàn)炫酷的旋轉(zhuǎn)星空效果示例

更新時(shí)間：2019年02月13日 12:10:17 作者：測(cè)試貓

這篇文章主要介紹了JS+canvas畫布實(shí)現(xiàn)炫酷的旋轉(zhuǎn)星空效果,結(jié)合實(shí)例形式分析了js結(jié)合HTML5 canvas圖形繪制與數(shù)值計(jì)算相關(guān)操作技巧,需要的朋友可以參考下

本文實(shí)例講述了JS+canvas畫布實(shí)現(xiàn)炫酷的旋轉(zhuǎn)星空效果。分享給大家供大家參考，具體如下：

canvas是html5的新標(biāo)簽，其畫布功能尤為強(qiáng)大。當(dāng)然了canvas在IE10以下瀏覽器是不兼容的，所以呢為了特效肯定是犧牲一定的兼容性。這里呢，分享一個(gè)基于canvas開發(fā)的浩瀚星河插件，其實(shí)這個(gè)源代碼是網(wǎng)上下載的，我把它整合了一下，重新封裝一些參數(shù)提供更多的可改項(xiàng)。

首先引入兩個(gè)javascript腳本，一個(gè)是jquery插件，另一個(gè)是封裝好的cosmos_canvas.js

<script src="js/jquery-1.11.0.js" type="text/javascript" charset="utf-8"></script>
<script src="canvas/cosmos_canvas.js" type="text/javascript" charset="utf-8"></script>

HTML，當(dāng)然如果瀏覽器不支持canvas的話，運(yùn)行程序沒效果，并顯示“該瀏覽器不支持canvas”

<canvas id="starts">該瀏覽器不支持canvas</canvas>

cosmos_canvas.js腳本

function canvas(id,starscolor,starsamount,starsradius,movrange,speed,trailing){
  //宇宙特效
"use strict";
var canvas = document.getElementById(id),
 ctx = canvas.getContext('2d'),
 w = canvas.width = window.innerWidth,
 h = canvas.height = window.innerHeight,
 hue = starscolor,//230
 stars = [],
 count = 0,
 maxStars = starsamount;//星星數(shù)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 / movrange;
 //星星移動(dòng)范圍，值越大范圍越小，
}
var Star = function() {
 this.orbitRadius = random(maxOrbit(w, h));
 this.radius = random(starsradius, this.orbitRadius) / 8;
 //星星半徑大小
 this.orbitX = w / 2;
 this.orbitY = h / 2;
 this.timePassed = random(0, maxStars);
 this.speed = random(this.orbitRadius) / speed;
 //星星移動(dòng)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 = trailing; //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();
}

調(diào)用方法：這里沒寫任何樣式所以默認(rèn)情況下是全屏效果

$(function(){
//canvas的id名，星星顏色(hsla的hue色調(diào))，星星數(shù)量，星星半徑比，星星移動(dòng)范圍(值越大范圍越小)，星星移動(dòng)速度(值越大速度越慢),星星拖尾效果(0~1值越小拖尾越明顯)
canvas("starts",230,1000,60,2,50000,0.5);
});

效果：

然后我再加3個(gè)canvas，改些參數(shù)做效果對(duì)比吧

HTML

<canvas id="starts">該瀏覽器不支持canvas</canvas>
<canvas id="starts1">該瀏覽器不支持canvas</canvas>
<canvas id="starts2">該瀏覽器不支持canvas</canvas>
<canvas id="starts3">該瀏覽器不支持canvas</canvas>

javascript

$(function(){
  //canvas的id名，星星顏色(hsla的hue色調(diào))，星星數(shù)量，星星半徑比，星星移動(dòng)范圍(值越大范圍越小)，星星移動(dòng)速度(值越大速度越慢),星星拖尾效果(0~1值越小拖尾越明顯)
  canvas("starts",230,1000,60,2,50000,0.5);
  canvas("starts1",160,800,70,2.5,55000,0.4);
  canvas("starts2",80,600,80,3,60000,0.3);
  canvas("starts3",0,400,90,3.5,65000,0.2);
  $("canvas").width($(window).width()/2);
  $("canvas").height($(window).height()/2);
  $("canvas").css("float","left");
});

就這樣，四個(gè)浩瀚的宇宙出來了