很漂亮的一个背景控件——ribbons.js

　　写博客的人都喜欢优化自己的博客主页，博主也一样，找了一些背景控件，像canvas-nest.js等等，最终选择了ribbons.js，并基于源码，稍作了一丁点的修改，这里分享出来　　　

    (function (name, factory) {
        if (typeof window === "object") {
            window[name] = factory();
        }
    })
        ("Ribbons", function () {
            var _w = window, _b = document.body, _d = document.documentElement;
 
            //随机函数
            var random = function () {
                if (arguments.length === 1) {
                    if (Array.isArray(arguments[0])) {
                        var index = Math.round(random(0, arguments[0].length - 1));
                        return arguments[0][index];
                    }
                    return random(0, arguments[0]);
                } else
                    if (arguments.length === 2) {
                        return Math.random() * (arguments[1] - arguments[0]) + arguments[0];
                    }
                return 0;
            };
 
            //屏幕信息
            var screenInfo = function (e) {
                var width = Math.max(0, _w.innerWidth || _d.clientWidth || _b.clientWidth || 0),
                    height = Math.max(0, _w.innerHeight || _d.clientHeight || _b.clientHeight || 0),
                    scrollx = Math.max(0, _w.pageXOffset || _d.scrollLeft || _b.scrollLeft || 0) - (_d.clientLeft || 0),
                    scrolly = Math.max(0, _w.pageYOffset || _d.scrollTop || _b.scrollTop || 0) - (_d.clientTop || 0);
                return {
                    width: width,
                    height: height,
                    ratio: width / height,
                    centerx: width / 2,
                    centery: height / 2,
                    scrollx: scrollx,
                    scrolly: scrolly
                };
            };
 
            var mouseInfo = function (e) {
                var screen = screenInfo(e),
                    mousex = e ? Math.max(0, e.pageX || e.clientX || 0) : 0,
                    mousey = e ? Math.max(0, e.pageY || e.clientY || 0) : 0;
 
                return {
                    mousex: mousex,
                    mousey: mousey,
                    centerx: mousex - screen.width / 2,
                    centery: mousey - screen.height / 2
                };
            };
 
            //点
            var Point = function (x, y) {
                this.x = 0;
                this.y = 0;
                this.set(x, y);
            };
            //点运算
            Point.prototype = {
                constructor: Point,
                set: function (x, y) {
                    this.x = x || 0; this.y = y || 0;
                },
                copy: function (point) {
                    this.x = point.x || 0; this.y = point.y || 0; return this;
                },
                multiply: function (x, y) {
                    this.x *= x || 1; this.y *= y || 1; return this;
                },
                divide: function (x, y) {
                    this.x /= x || 1; this.y /= y || 1; return this;
                },
                add: function (x, y) {
                    this.x += x || 0; this.y += y || 0; return this;
                },
                subtract: function (x, y) {
                    this.x -= x || 0; this.y -= y || 0; return this;
                },
                clampX: function (min, max) {
                    this.x = Math.max(min, Math.min(this.x, max)); return this;
                },
                clampY: function (min, max) {
                    this.y = Math.max(min, Math.min(this.y, max)); return this;
                },
                flipX: function () {
                    this.x *= -1; return this;
                },
                flipY: function () {
                    this.y *= -1; return this;
                }
            };
 
            //丝带画板
            var Factory = function (options) {
                this._canvas = null;
                this._context = null;
                this._sto = null;
                this._width = 0;
                this._height = 0;
                this._scroll = 0;
                this._ribbons = [];
                this._options = {
                    id: "bgCanvas",//画板Id
                    backgroundColor: "#1f1f1f",//画板背景
                    colorSaturation: "80%",//纯度
                    colorBrightness: "60%",//亮度
                    colorAlpha: 0.65,//透明度
                    colorCycleSpeed: 6,//丝带不同块之间的色彩变化量
                    verticalPosition: "center",//丝带相对于屏幕的初始位置：top/min 屏幕最上方，middle|center 中间，bottom|max 屏幕最下面
                    horizontalSpeed: 200,//丝带水平方向移动速度参数（会乘以一个随机值）
                    ribbonCount: 3,//同一时间丝带总条数
                    strokeSize: 0,//公共边路径样式
                    parallaxAmount: -0.5,//滚动偏移参数，-1表示不偏移，0表示基于丝带只出现在页面最上面
                    animateSections: true//丝带块是否偏移，显得有动感
                };
                this._onDraw = this._onDraw.bind(this);
                this._onResize = this._onResize.bind(this);
                this._onScroll = this._onScroll.bind(this);
                this.setOptions(options);
                this.init();
            };
            Factory.prototype = {
                constructor: Factory,
                setOptions: function (options) {
                    if (typeof options === "object") {
                        for (var key in options) {
                            if (options.hasOwnProperty(key)) {
                                this._options[key] = options[key];
                            }
                        }
                    }
                },
                //初始化
                init: function () {
                    //初始化画板
                    try {
                        this._canvas = document.createElement("canvas");
                        this._canvas.style["display"] = "block";
                        this._canvas.style["position"] = "fixed";
                        this._canvas.style["margin"] = "0";
                        this._canvas.style["padding"] = "0";
                        this._canvas.style["border"] = "0";
                        this._canvas.style["outline"] = "0";
                        this._canvas.style["left"] = "0";
                        this._canvas.style["top"] = "0";
                        this._canvas.style["width"] = "100%";
                        this._canvas.style["height"] = "100%";
                        this._canvas.style["z-index"] = "-1";
                        this._canvas.style["background-color"] = this._options.backgroundColor;
                        this._canvas.id = this._options.id;
                        this._onResize();
                        this._context = this._canvas.getContext("2d");
                        this._context.clearRect(0, 0, this._width, this._height);
                        this._context.globalAlpha = this._options.colorAlpha;
                        window.addEventListener("resize", this._onResize);
                        window.addEventListener("scroll", this._onScroll);
                        document.body.appendChild(this._canvas);
                    }
                    catch (e) {
                        console.warn("Canvas Context Error: " + e.toString());
                        return;
                    }
                    //开始绘画
                    this._onDraw();
                },
                //生成一条丝带
                addRibbon: function () {
                    var dir = Math.round(random(1, 9)) > 5 ? "right" : "left",//丝带延伸方向
                        stop = 1000,
                        hide = 200,
                        min = 0 - hide,
                        max = this._width + hide,
                        movex = 0,
                        movey = 0,
                        startx = dir === "right" ? min : max,//起始点x左边
                        starty = Math.round(random(0, this._height));//起始点y左边
 
                    //丝带生成的位置
                    if (/^(top|min)$/i.test(this._options.verticalPosition)) {//最上方
                        starty = 0 + hide;
                    } else if (/^(middle|center)$/i.test(this._options.verticalPosition)) {//中间
                        starty = this._height / 2;
                    } else if (/^(bottom|max)$/i.test(this._options.verticalPosition)) {//最下方
                        starty = this._height - hide;
                    }
 
                    if (this._options.parallaxAmount !== 0) {
                        starty += this._scroll;//加上滚动
                    }
 
                    var ribbon = [],
                        point1 = new Point(startx, starty),
                        point2 = new Point(startx, starty),
                        point3 = null,
                        color = Math.round(random(0, 360)),
                        delay = 0;
 
                    //从起始位置开始生成一条丝带
                    //丝带每个分部都是一个三角形，三点确定一个三角形，相邻三角形有一条公共边
                    while (true) {
                        if (stop <= 0) break;
                        stop--;
                        movex = Math.round((Math.random() * 1 - 0.2) * this._options.horizontalSpeed);
                        movey = Math.round((Math.random() * 1 - 0.5) * (this._height * 0.25));
                        point3 = new Point();
                        point3.copy(point2);
                        if (dir === "right") {
                            point3.add(movex, movey);
                            if (point2.x >= max) break;
                        } else if (dir === "left") {
                            point3.subtract(movex, movey);
                            if (point2.x <= min) break;
                        }
                        ribbon.push({
                            //三点
                            point1: new Point(point1.x, point1.y),
                            point2: new Point(point2.x, point2.y),
                            point3: point3,
                            color: color,//丝带颜色
                            delay: delay,//延迟消失
                            dir: dir,//方向
                            alpha: 0,//透明度
                            phase: 0 //随机位移有关参数
                        });
                        //公共边
                        point1.copy(point2);
                        point2.copy(point3);
                        delay += 4;
                        color += this._options.colorCycleSpeed;
                    }
                    this._ribbons.push(ribbon);
                },
                //绘制一个三角形方块
                _drawRibbonSection: function (section) {
                    if (section) {
                        if (section.phase >= 1 && section.alpha <= 0) {
                            return true;
                        }
                        if (section.delay <= 0) {
                            section.phase += 0.02;
                            section.alpha = Math.sin(section.phase) * 1;
                            section.alpha = section.alpha <= 0 ? 0 : section.alpha;
                            section.alpha = section.alpha >= 1 ? 1 : section.alpha;
                            if (this._options.animateSections) {
                                var mod = Math.sin(1 + section.phase * Math.PI / 2) * 0.1;
                                if (section.dir === "right") {
                                    section.point1.add(mod, 0);
                                    section.point2.add(mod, 0);
                                    section.point3.add(mod, 0);
                                } else {
                                    section.point1.subtract(mod, 0);
                                    section.point2.subtract(mod, 0);
                                    section.point3.subtract(mod, 0);
                                }
                                section.point1.add(0, mod);
                                section.point2.add(0, mod);
                                section.point3.add(0, mod);
                            }
                        } else {
                            section.delay -= 0.5;
                        }
                        var s = this._options.colorSaturation,
                            l = this._options.colorBrightness,
                            c = "hsla(" + section.color + ", " + s + ", " + l + ", " + section.alpha + " )";
 
                        //绘制一个方块
                        this._context.save();
                        if (this._options.parallaxAmount !== 0) {
                            this._context.translate(0, this._scroll * this._options.parallaxAmount);
                        }
                        this._context.beginPath();
                        this._context.moveTo(section.point1.x, section.point1.y);
                        this._context.lineTo(section.point2.x, section.point2.y);
                        this._context.lineTo(section.point3.x, section.point3.y);
                        this._context.fillStyle = c;
                        this._context.fill();
                        if (this._options.strokeSize > 0) {
                            this._context.lineWidth = this._options.strokeSize;
                            this._context.strokeStyle = c;
                            this._context.lineCap = "round";
                            this._context.stroke();
                        }
                        this._context.restore();
                    }
                    return false;
                },
                //绘制丝带
                _onDraw: function () {
                    //清空已经绘制过的丝带
                    for (var i = 0, t = this._ribbons.length; i < t; ++i) {
                        if (!this._ribbons[i]) {
                            this._ribbons.splice(i, 1);
                        }
                    }
                    this._context.clearRect(0, 0, this._width, this._height);//清空画板
                    for (var a = 0; a < this._ribbons.length; ++a) {
                        var ribbon = this._ribbons[a],
                            numSections = ribbon ? ribbon.length : 0,
                            numDone = 0;
 
                        //绘制整条丝带
                        for (var b = 0; b < numSections; ++b) {
                            if (this._drawRibbonSection(ribbon[b])) {
                                numDone++;
                            }
                        }
                        //丝带已经全部飘过屏幕，设置为null,函数前面会自动清理
                        if (numDone >= numSections) {
                            this._ribbons[a] = null;
                        }
                    }
                    //随机生成一条丝带
                    if (this._ribbons.length < this._options.ribbonCount && Math.random() > 0.99) {
                        this.addRibbon();
                    }
 
                    //调度交给系统，当需要刷新画板时调用指定的回调函数，用于提高性能
                    requestAnimationFrame(this._onDraw);
                },
                //重新设置窗体大小时需要获取窗体大小
                _onResize: function (e) {
                    var screen = screenInfo(e);
                    this._width = screen.width;
                    this._height = screen.height;
                    if (this._canvas) {
                        this._canvas.width = this._width;
                        this._canvas.height = this._height;
                        if (this._context) {
                            this._context.globalAlpha = this._options.colorAlpha;
                        }
                    }
                },
                //滚动时获取滚动距离
                _onScroll: function (e) {
                    var screen = screenInfo(e);
                    this._scroll = screen.scrolly;
                }
            }; return Factory;
        });
 
    //初始化并绘制
    new Ribbons({
        ribbonCount: 5,
        parallaxAmount: -0.99
    });

　　注意，在代码的最后面有丝带的初始化　　

    //初始化并绘制
    new Ribbons({
        ribbonCount: 5,
        parallaxAmount: -0.99
    });

　　里面可以传的参数有　　

    options = {
        id: "bgCanvas",//画板Id
        backgroundColor: "#1f1f1f",//画板背景
        colorSaturation: "80%",//纯度
        colorBrightness: "60%",//亮度
        colorAlpha: 0.65,//透明度
        colorCycleSpeed: 6,//丝带不同块之间的色彩变化量
        verticalPosition: "center",//丝带相对于屏幕的初始位置：top/min 屏幕最上方，middle|center 中间，bottom|max 屏幕最下面
        horizontalSpeed: 200,//丝带水平方向移动速度参数（会乘以一个随机值）
        ribbonCount: 3,//同一时间丝带总条数
        strokeSize: 0,//公共边路径样式
        parallaxAmount: -0.5,//滚动偏移参数，-1表示不偏移，0表示基于丝带只出现在页面最上面
        animateSections: true//丝带块是否偏移，显得有动感
    };

　　另外这个部分初始化代码可以提取出来放到其他地方去初始化，比如window的onload里面，这里直接这么写是为了将上面的代码封装到一个js文件中，然后直接引用js文件即可，但是注意一下，这里最好在body的最后面引用，否则可能会导致一些页面加载不全导致的问题，如新建一个html文件：　　

    <!DOCTYPE html>
    <html>
    <head>
        <meta charset="utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <title>Ribbons</title>
    </head>
    <body>
　　　　 <!--这里最好在body的最后面引用js文件-->
        <!--本地-->
        <script src="ribbons.js"></script>
        <!--远程-->
        <!--<script src="https://blog-static.cnblogs.com/files/shanfeng1000/ribbons.js"></script>-->
    </body>
    </html>

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