山大网安靶场实验平台项目-个人记录（八）之动态背景

系列文章专栏地址:

山东大学网络安全靶场实验平台

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本期内容： 设置网站动态背景

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一、前言

当前项目，需要对背景风格进行统一（美化？）
我寻找到了一个动态的背景图，然后改一改应用到网站上。
先提一下，我们当前的背景主要是渐变色背景图，
CSS代码如下：设置背景图片（起始颜色，终止颜色）

  background-image: linear-gradient(to bottom right, #000000, 	#483D8B);

二、代码设计

先贴上动态背景文件的完整代码，是 .js 文件

const animation  =()=> {
    //封装方法，压缩之后减少文件大小
    function get_attribute(node, attr, default_value) {
        return node.getAttribute(attr) || default_value;
    }
    //封装方法，压缩之后减少文件大小
    function get_by_tagname(name) {
        return document.getElementsByTagName(name);
    }
    //获取配置参数
    function get_config_option() {
        var scripts = get_by_tagname("script"),
            script_len = scripts.length,
            script = scripts[script_len - 1]; //当前加载的script
        return {
            l: script_len, //长度，用于生成id用
            z: get_attribute(script, "zIndex", -1), //z-index
            o: get_attribute(script, "opacity", 10000), //opacity
            c: get_attribute(script, "color", "255,255,255"), //color
            n: get_attribute(script, "count", 100), //count
        };
    }
    //设置canvas的高宽
    function set_canvas_size() {
        document.body.style.backgroundColor= 'black';
        (canvas_width = the_canvas.width =
            window.innerWidth ||
            document.documentElement.clientWidth ||
            document.body.clientWidth),
            (canvas_height = the_canvas.height =
                window.innerHeight||
                document.documentElement.clientHeight ||
                document.body.clientHeight);
    }

    //绘制过程
    function draw_canvas() {
        context.clearRect(0, 0, canvas_width, canvas_height);
        //随机的线条和当前位置联合数组
        var e, i, d, x_dist, y_dist, dist; //临时节点
        //遍历处理每一个点
        random_lines.forEach(function (r, idx) {
            (r.x += r.xa),
                (r.y += r.ya), //移动
                (r.xa *= r.x > canvas_width || r.x < 0 ? -1 : 1),
                (r.ya *= r.y > canvas_height || r.y < 0 ? -1 : 1), //碰到边界，反向反d
                context.fillRect(r.x - 0.5, r.y - 0.5, 1, 1); //绘制一个宽高为1的点
            //从下一个点开始
            for (i = idx + 1; i < all_array.length; i++) {
                e = all_array[i];
                //不是当前点
                if (null !== e.x && null !== e.y) {
                    (x_dist = r.x - e.x), //x轴距离 l
                        (y_dist = r.y - e.y), //y轴距离 n
                        (dist = x_dist * x_dist + y_dist * y_dist); //总距离, m
                    dist < e.max &&
                    (e === current_point &&
                    dist >= e.max / 2 &&
                    ((r.x -= 0.03 * x_dist), (r.y -= 0.03 * y_dist)), //靠近的时候加速
                        (d = (e.max - dist) / e.max),
                        context.beginPath(),
                        (context.lineWidth = d ),
                        (context.strokeStyle = "rgba(" + config.c + "," + (d + 0.9) + ")"),
                        context.moveTo(r.x, r.y),
                        context.lineTo(e.x, e.y),
                        context.stroke());
                }

            }
        }),
            frame_func(draw_canvas);
    }

    //清空画布
    // var cxt=document.getElementById("myCanvas").getContext("2d"),
    // nowwidth =window.innerWidth ||document.documentElement.clientWidth ||document.body.clientWidth,
    // nowheight = window.innerHeight||document.documentElement.clientHeight || document.body.clientHeight;
    // cxt.clearRect(0,0,nowwidth,nowheight);

    //创建画布，并添加到body中
    var the_canvas = document.createElement("canvas"), //画布
        config = get_config_option(), //配置
        canvas_id = "c_n" + config.l, //canvas id
        context = the_canvas.getContext("2d"),
        canvas_width,
        canvas_height,
        frame_func =
            window.requestAnimationFrame ||
            window.webkitRequestAnimationFrame ||
            window.mozRequestAnimationFrame ||
            window.oRequestAnimationFrame ||
            window.msRequestAnimationFrame ||
            function (func) {
                window.setTimeout(func, 1000 / 45);
            },
        random = Math.random,
        current_point = {
            x: null, //当前鼠标x
            y: null, //当前鼠标y
            max: 20000,
        },
        all_array;
    the_canvas.id = canvas_id;
    the_canvas.style.cssText =
        "position:fixed;top:0;left:0;z-index:" + config.z + ";opacity:" + config.o;
    get_by_tagname("body")[0].appendChild(the_canvas);
    //初始化画布大小

    set_canvas_size(), (window.onresize = set_canvas_size);
    //当时鼠标位置存储，离开的时候或者过几秒，释放当前位置信息

    (window.onmousemove = function (e) {
        (e = e || window.event),
            (current_point.x = e.clientX),
            (current_point.y = e.clientY>70?e.clientY:null);
    }),(window.onmousedown = function () {
        (current_point.x = null), (current_point.y = null);
    }),(window.onmouseout = function () {
        (current_point.x = null), (current_point.y = null);
    });
    //随机生成config.n条线位置信息
    for (var random_lines = [], i = 0; config.n > i; i++) {
        var x = random() * canvas_width, //随机位置
            y = random() * canvas_height,
            xa = 2 * random() - 1, //随机运动方向
            ya = 2 * random() - 1;
        random_lines.push({
            x: x,
            y: y,
            xa: xa,
            ya: ya,
            max: 6000, //沾附距离
        });
    }
    all_array = random_lines.concat([current_point]);
    //0.1秒后绘制
    setTimeout(function () {
        draw_canvas();
    }, 100);
}
export default animation

语句分析：

前面定义若干函数，后面是主内容

    function set_canvas_size() {
        document.body.style.backgroundColor= 'black';
        (canvas_width = the_canvas.width =
            window.innerWidth ||
            document.documentElement.clientWidth ||
            document.body.clientWidth),
            (canvas_height = the_canvas.height =
                window.innerHeight||
                document.documentElement.clientHeight ||
                document.body.clientHeight);
    }

这个函数设置了画布的高度和宽度，但注意画布是从（0，0）开始的

    function get_config_option() {
        var scripts = get_by_tagname("script"),
            script_len = scripts.length,
            script = scripts[script_len - 1]; //当前加载的script
        return {
            l: script_len, //长度，用于生成id用
            z: get_attribute(script, "zIndex", -1), //z-index
            o: get_attribute(script, "opacity", 10000), //opacity
            c: get_attribute(script, "color", "255,255,255"), //color
            n: get_attribute(script, "count", 100), //count
        };
    }

这个函数定义了几个重要的参数，其中颜色不必多说，最后参数一个是控制生成点的数量。

这里定义了线的宽度。

使用这个js的方法如下：
在.vue文件中引入这个js文件，然后再created中调用它即可。

import animation from "../assets/js/background_black";
export default {
  name: "Home",
  components: {
  },
  created() {
    animation()
  },
}

三、结果展示

背景是不断漂浮移动并会聚集在鼠标处的线段