使用js实现动态背景 js动态设置背景图片 |
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本文实例为大家分享了js实现动态背景的具体代码，供大家参考，具体内容如下 1.将下面的代码复制并存为js文件 window.onload = function () { //定义body的margin由默认值8px->0px document.body.style.margin = "0"; document.body.style.background = "#30333F"; //创建canvas画布 document.body.appendChild(document.createElement("canvas")); var canvas = document.querySelector("canvas"), ctx = canvas.getContext("2d") //ctx返回一个在canvas上画图的api/dom canvas.width = window.innerWidth; canvas.height = window.innerHeight; canvas.style.position = "fixed"; ctx.lineWidth = .3; ctx.strokeStyle = (new Color(150)).style; //定义鼠标覆盖范围 var mousePosition = { x: 30 * canvas.width / 100, y: 30 * canvas.height / 100 }; var dots = { nb: 1000,//Dot的总数 distance: 50, d_radius: 100, array: [] }; //创建颜色类，Color类返回字符串型rgba（*,*,*,.8） function mixComponents(comp1, weight1, comp2, weight2) { return (comp1 * weight1 + comp2 * weight2) / (weight1 + weight2); } function averageColorStyles(dot1, dot2) { var color1 = dot1.color, color2 = dot2.color; var r = mixComponents(color1.r, dot1.radius, color2.r, dot2.radius), g = mixComponents(color1.g, dot1.radius, color2.g, dot2.radius), b = mixComponents(color1.b, dot1.radius, color2.b, dot2.radius); return createColorStyle(Math.floor(r), Math.floor(g), Math.floor(b)); } function colorValue(min) { return Math.floor(Math.random() * 255 + min); } function createColorStyle(r, g, b) { return "rgba(" + r + "," + g + "," + b + ", 0.8)"; } function Color(min) { min = min || 0; this.r = colorValue(min); this.g = colorValue(min); this.b = colorValue(min); this.style = createColorStyle(this.r, this.g, this.b); } //创建Dot类以及一系列方法 function Dot() { this.x = Math.random() * canvas.width; this.y = Math.random() * canvas.height; this.vx = -.5 + Math.random(); this.vy = -.5 + Math.random(); this.radius = Math.random() * 2; this.color = new Color(); } Dot.prototype = { draw: function () { ctx.beginPath(); ctx.fillStyle = this.color.style; ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, false); ctx.fill(); } }; function moveDots() {//Dot对象的移动 for (i = 0; i < dots.nb; i++) { var dot = dots.array[i]; if (dot.y < 0 || dot.y > canvas.height) { dot.vx = dot.vx; dot.vy = - dot.vy; } else if (dot.x < 0 || dot.x > canvas.width) { dot.vx = - dot.vx; dot.vy = dot.vy; } dot.x += dot.vx; dot.y += dot.vy; } } function connectDots() {//DOt对象的连接 for (i = 0; i < dots.nb; i++) { for (j = i; j < dots.nb; j++) { i_dot = dots.array[i]; j_dot = dots.array[j]; if ((i_dot.x - j_dot.x) < dots.distance && (i_dot.y - j_dot.y) < dots.distance && (i_dot.x - j_dot.x) > - dots.distance && (i_dot.y - j_dot.y) > - dots.distance) { if ((i_dot.x - mousePosition.x) < dots.d_radius && (i_dot.y - mousePosition.y) < dots.d_radius && (i_dot.x - mousePosition.x) > - dots.d_radius && (i_dot.y - mousePosition.y) > - dots.d_radius) { ctx.beginPath(); ctx.strokeStyle = averageColorStyles(i_dot, j_dot); ctx.moveTo(i_dot.x, i_dot.y); ctx.lineTo(j_dot.x, j_dot.y); ctx.stroke();//绘制定义的路线 ctx.closePath();//创建从当前点回到起始点的路径 } } } } } function createDots() {//创建nb个Dot对象 for (i = 0; i < dots.nb; i++) { dots.array.push(new Dot()); } } function drawDots() {//引用Dot原型链，使用draw方法，在canvas上画出Dot对象 for (i = 0; i < dots.nb; i++) { var dot = dots.array[i]; dot.draw(); } } function animateDots() { ctx.clearRect(0, 0, canvas.width, canvas.height);//清除画布，否则线条会连在一起 moveDots(); connectDots(); drawDots(); requestAnimationFrame(animateDots); } createDots();//使用创建Dot类函数 requestAnimationFrame(animateDots);//使用canvas独有的60Hz刷新屏幕画布的方法 document.querySelector("canvas").addEventListener("mousemove", function (e) { mousePosition.x = e.pageX; mousePosition.y = e.pageY; }) document.querySelector("canvas").addEventListener("mouseleave", function (e) {//鼠标离开时，连接自动返回到画布中心 mousePosition.x = canvas.width / 2; mousePosition.y = canvas.height / 2; }) }2.然后在需要使用动态背景的html页面引入js文件就可以了 效果如下： |
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