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

2019-11-19 12:08:58

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供稿：網(wǎng)友

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 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;}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