HTML5 CSS3 诱人的实例：canvas 模拟实现电子彩票刮刮乐-白红宇

HTML5 CSS3 诱人的实例：canvas 模拟实现电子彩票刮刮乐

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发布时间：2019-06-26

本文共 9521 字，大约阅读时间需要 31 分钟。

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今天给大家带来一个刮刮乐的小样例~基于HTML5 canvas的，有兴趣的能够改成android版本号的。或者其它的~

效果图：

贴一张我中500w的照片。咋办啊，怎么花呢~

好了，以下開始原理：

1、刮奖区域两个Canvas。一个是front ，一个back 。front遮盖住以下的canvas。

2、canvas默认填充了一个矩形，将以下canvas效果图遮盖，然后监听mouse事件。依据mousemove的x,y坐标。进行擦出front canvas上的矩形区域，然后显示出以下的canvas的效果图。

非常easy把~嘿嘿~

1、HTML文件内容：

2、首先我利用了一个曾经写的canvas辅助类。留下来今天要用的一些方法：

/** * Created with JetBrains WebStorm. * User: zhy * Date: 13-12-17 * Time: 下午9:42 * To change this template use File | Settings | File Templates. */function Canvas2D($canvas){    var context = $canvas[0].getContext("2d"),        width = $canvas[0].width,        height = $canvas[0].height,        pageOffset = $canvas.offset();    context.font = "24px Verdana, Geneva, sans-serif";    context.textBaseline = "top";    /**     * 绘制矩形     * @param start     * @param end     * @param isFill     */    this.drawRect = function (start, end, isFill)    {        var w = end.x - start.x , h = end.y - start.y;        if (isFill)        {            context.fillRect(start.x, start.y, w, h);        }        else        {            context.strokeRect(start.x, start.y, w, h);        }    };    /**     * 依据书写的文本，得到该文本在canvas上书写的中心位置的左上角坐标     * @param text     * @returns {
    {x: number, y: number}}     */    this.caculateTextCenterPos = function (text)    {        var metrics = context.measureText(text);        console.log(metrics);//        context.font = fontSize + "px Verdana, Geneva, sans-serif";        var textWidth = metrics.width;        var textHeight = parseInt(context.font);        return {            x: width / 2 - textWidth / 2,            y: height / 2 - textHeight / 2        };    }    this.width = function ()    {        return width;    }    this.height = function ()    {        return height;    }    this.resetOffset = function ()    {        pageOffset = $canvas.offset();    }    /**     * 当屏幕大小发生变化，又一次计算offset     */    $(window).resize(function ()    {        pageOffset = $canvas.offset();    });    /**     * 将页面上的左边转化为canvas中的坐标     * @param pageX     * @param pageY     * @returns {
    {x: number, y: number}}     */    this.getCanvasPoint = function (pageX, pageY)    {        return{            x: pageX - pageOffset.left,            y: pageY - pageOffset.top        }    }    /**     * 清除区域，此用户鼠标擦出刮奖涂层     * @param start     * @returns {*}     */    this.clearRect = function (start)    {        context.clearRect(start.x, start.y, 10, 10);        return this;    };    /**     *将文本绘制到canvas的中间     * @param text     * @param fill     */    this.drawTextInCenter = function (text, fill)    {        var point = this.caculateTextCenterPos(text);        if (fill)        {            context.fillText(text, point.x, point.y);        }        else        {            context.strokeText(text, point.x, point.y);        }    };    /**     * 设置画笔宽度     * @param newWidth     * @returns {*}     */    this.penWidth = function (newWidth)    {        if (arguments.length)        {            context.lineWidth = newWidth;            return this;        }        return context.lineWidth;    };    /**     * 设置画笔颜色     * @param newColor     * @returns {*}     */    this.penColor = function (newColor)    {        if (arguments.length)        {            context.strokeStyle = newColor;            context.fillStyle = newColor;            return this;        }        return context.strokeStyle;    };    /**     * 设置字体大小     * @param fontSize     * @returns {*}     */    this.fontSize = function (fontSize)    {        if (arguments.length)        {            context.font = fontSize + "px Verdana, Geneva, sans-serif";            return this;        }        return context.fontSize;    }}

这个类也就对Canvas对象进行了简单的封装，设置參数。绘制图形什么的。比較简单，大家能够完好下这个类~

3、GuaGuaLe.js

/** * Created with JetBrains WebStorm. * User: zhy * Date: 14-6-24 * Time: 上午11:36 * To change this template use File | Settings | File Templates. */function GuaGuaLe(idFront, idBack){    this.$eleBack = $("#" + idBack);    this.$eleFront = $("#" + idFront);    this.frontCanvas = new Canvas2D(this.$eleFront);    this.backCanvas = new Canvas2D(this.$eleBack);    this.isStart = false;}GuaGuaLe.prototype = {    constructor: GuaGuaLe,    /**     * 将用户的传入的參数和默认參数做合并     * @param desAttr     * @returns {
    {frontFillColor: string, backFillColor: string, backFontColor: string, backFontSize: number, msg: string}}     */    mergeAttr: function (desAttr)    {        var defaultAttr = {            frontFillColor: "silver",            backFillColor: "gold",            backFontColor: "red",            backFontSize: 24,            msg: "谢谢惠顾"        };        for (var p in  desAttr)        {            defaultAttr[p] = desAttr[p];        }        return defaultAttr;    },    init: function (desAttr)    {        var attr = this.mergeAttr(desAttr);        //初始化canvas        this.backCanvas.penColor(attr.backFillColor);        this.backCanvas.fontSize(attr.backFontSize);        this.backCanvas.drawRect({x: 0, y: 0}, {x: this.backCanvas.width(), y: this.backCanvas.height()}, true);        this.backCanvas.penColor(attr.backFontColor);        this.backCanvas.drawTextInCenter(attr.msg, true);        //初始化canvas        this.frontCanvas.penColor(attr.frontFillColor);        this.frontCanvas.drawRect({x: 0, y: 0}, {x: this.frontCanvas.width(), y: this.frontCanvas.height()}, true);        var _this = this;        //设置事件        this.$eleFront.mousedown(function (event)        {            _this.mouseDown(event);        }).mousemove(function (event)            {                _this.mouseMove(event);            }).mouseup(function (event)            {                _this.mouseUp(event);            });    },    mouseDown: function (event)    {        this.isStart = true;        this.startPoint = this.frontCanvas.getCanvasPoint(event.pageX, event.pageY);    },    mouseMove: function (event)    {        if (!this.isStart)return;        var p = this.frontCanvas.getCanvasPoint(event.pageX, event.pageY);        this.frontCanvas.clearRect(p);    },    mouseUp: function (event)    {        this.isStart = false;    }};

通过用户传入的两个canvas的id，然后生成一个对象，进行初始化操作，设置事件。当然了也提供用户设置可选的參数。各种颜色，已经刮开后显示的信息等，通过{

frontFillColor: "silver",

backFillColor: "gold",

backFontColor: "red",

backFontSize: 24,

msg: "谢谢惠顾"

};传给init方法进行设置。

好了，然后就基本完工了，測试一下：

基本实现了刮开图层，可是存在一个小问题，就是当用户滑动特别快时，会出现一些断点，当然也能够忽略，只是我们准备提供一下解决方式：

产生原因：因为鼠标移动速度过快，产生的断点。解决方式：将mousemove中两次的鼠标左边，进行拆分成多个断点坐标：

如上图，把两点之间进行连线，依据斜率。然后分成多个小段，分别获得线段上的坐标（有四种可能。有兴趣能够画绘图，计算下。代码例如以下）：

var k;        if (p.x > this.startPoint.x)        {            k = (p.y - this.startPoint.y) / (p.x - this.startPoint.x);            for (var i = this.startPoint.x; i < p.x; i += 5)            {                this.frontCanvas.clearRect({x: i, y: (this.startPoint.y + (i - this.startPoint.x) * k)});            }        } else        {            k = (p.y - this.startPoint.y) / (p.x - this.startPoint.x);            for (var i = this.startPoint.x; i > p.x; i -= 5)            {                this.frontCanvas.clearRect({x: i, y: (this.startPoint.y + ( i - this.startPoint.x  ) * k)});            }        }        this.startPoint = p;

4、最后贴一下完整的GuaGuaLe.js

/** * Created with JetBrains WebStorm. * User: zhy * Date: 14-6-24 * Time: 上午11:36 * To change this template use File | Settings | File Templates. */function GuaGuaLe(idFront, idBack){    this.$eleBack = $("#" + idBack);    this.$eleFront = $("#" + idFront);    this.frontCanvas = new Canvas2D(this.$eleFront);    this.backCanvas = new Canvas2D(this.$eleBack);    this.isStart = false;}GuaGuaLe.prototype = {    constructor: GuaGuaLe,    /**     * 将用户的传入的參数和默认參数做合并     * @param desAttr     * @returns {
    {frontFillColor: string, backFillColor: string, backFontColor: string, backFontSize: number, msg: string}}     */    mergeAttr: function (desAttr)    {        var defaultAttr = {            frontFillColor: "silver",            backFillColor: "gold",            backFontColor: "red",            backFontSize: 24,            msg: "谢谢惠顾"        };        for (var p in  desAttr)        {            defaultAttr[p] = desAttr[p];        }        return defaultAttr;    },    init: function (desAttr)    {        var attr = this.mergeAttr(desAttr);        //初始化canvas        this.backCanvas.penColor(attr.backFillColor);        this.backCanvas.fontSize(attr.backFontSize);        this.backCanvas.drawRect({x: 0, y: 0}, {x: this.backCanvas.width(), y: this.backCanvas.height()}, true);        this.backCanvas.penColor(attr.backFontColor);        this.backCanvas.drawTextInCenter(attr.msg, true);        //初始化canvas        this.frontCanvas.penColor(attr.frontFillColor);        this.frontCanvas.drawRect({x: 0, y: 0}, {x: this.frontCanvas.width(), y: this.frontCanvas.height()}, true);        var _this = this;        //设置事件        this.$eleFront.mousedown(function (event)        {            _this.mouseDown(event);        }).mousemove(function (event)            {                _this.mouseMove(event);            }).mouseup(function (event)            {                _this.mouseUp(event);            });    },    mouseDown: function (event)    {        this.isStart = true;        this.startPoint = this.frontCanvas.getCanvasPoint(event.pageX, event.pageY);    },    mouseMove: function (event)    {        if (!this.isStart)return;        var p = this.frontCanvas.getCanvasPoint(event.pageX, event.pageY);        this.frontCanvas.clearRect(p);    },    mouseUp: function (event)    {        this.isStart = false;    }};

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好了，收工吃饭~

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