這篇文章主要介紹了JS+canvas畫布實現炫酷的旋轉星空效果,結合實例形式分析了js結合HTML5 canvas圖形繪製與數值計算相關操作技巧,需要的朋友可以參考下
本文實例講述了JS+canvas畫布實現炫酷的旋轉星空效果。分享給大家供大家參考，具體如下：
canvas是html5的新標籤，其畫布功能尤爲強大。當然了canvas在IE10以下瀏覽器是不兼容的，所以呢爲了特效肯定是犧牲一定的兼容性。這裏呢，分享一個基於canvas開發的浩瀚星河插件，其實這個源代碼是網上下載的，我把它整合了一下，重新封裝一些參數提供更多的可改項。
首先引入兩個javascript腳本，一個是jquery插件，另一個是封裝好的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，當然如果瀏覽器不支持canvas的話，運行程序沒效果，並顯示“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;
//星星移動範圍，值越大範圍越小，
}
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();
}
調用方法：這裏沒寫任何樣式所以默認情況下是全屏效果
$(function(){
//canvas的id名，星星顏色(hsla的hue色調)，星星數量，星星半徑比，星星移動範圍(值越大範圍越小)，星星移動速度(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：
然後我再加3個canvas，改些參數做效果對比吧
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)，星星數量，星星半徑比，星星移動範圍(值越大範圍越小)，星星移動速度(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，四個浩瀚的宇宙出來了
更多關於JavaScript相關內容還可查看本站專題：《JavaScript+HTML5特效與技巧彙總》、《JavaScript圖形繪製技巧總結》、《JavaScript錯誤與調試技巧總結》、《JavaScript數據結構與算法技巧總結》、《JavaScript遍歷算法與技巧總結》及《JavaScript數學運算用法總結》
希望本文所述對大家JavaScript程序設計有所幫助。