canvas 模拟实现电子彩票刮刮乐的代码

互联网 18-7-2

今天给大家带来一个刮刮乐的小例子~基于HTML5 canvas的,非常具有使用价值，有兴趣的可以了解一下。

今天给大家带来一个刮刮乐的小例子~基于HTML5 canvas的，有兴趣的可以改成Android版本的，或者其他的~

效果图：

贴一张我中500w的照片，咋办啊，怎么花呢~

好了，下面开始原理：

1、刮奖区域两个Canvas，一个是front ，一个back ，front遮盖住下面的canvas。

2、canvas默认填充了一个矩形，将下面canvas效果图遮盖，然后监听mouse事件，根据mousemove的x,y坐标，进行擦出front canvas上的矩形区域，然后显示出下面的canvas的效果图。

很简单把~嘿嘿~

1、HTML文件内容：

<!DOCTYPE html>   <html>   <head>       <title></title>       <meta charset="utf-8">          <script type="text/javascript" src="../../jquery-1.8.3.js"></script>       <script type="text/javascript" src="canvas2d.js"></script>          <script type="text/javascript" src="GuaGuaLe2.js"></script>          <script type="text/javascript">              $(function ()           {               var guaguale = new GuaGuaLe("front", "back");               guaguale.init({msg: "￥5000000.00"});           });       </script>       <style type="text/css">                 body           {               background: url("s_bd.jpg") repeat 0 0;           }              .container           {               position: relative;               width: 400px;               height: 160px;               margin: 100px auto 0;               background: url(s_title.png) no-repeat 0 0;               background-size: 100% 100%;           }              #front, #back           {               position: absolute;               width: 200px;               left: 50%;               top: 100%;               margin-left: -130px;               height: 80px;               border-radius: 5px;               border: 1px solid #444;           }          </style>      </head>   <body>      <p class="container">       <canvas id="back" width="200" height="80"></canvas>       <canvas id="front" width="200" height="80"></canvas>   </p>         </body>   </html>

2、首先我利用了一个以前写的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);           }       };          /**       * 根据书写的文本，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，重新计算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，设置参数，绘制图形什么的，比较简单，大家可以完善下这个类~

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.$eleBack);          this.isStart = false;      }      GuaGuaLe.prototype = {       constructor: GuaGuaLe,       /**       * 将用户的传入的参数和默认参数做合并       * @param desAttr       * @returns {{frontFillColor: string, backFillColor: string, backFontColor: string, backFontSize: number, msg: string}}       */       mergeAttr: function (desAttr)       {           var defaultAttr = {               frontFillColor: "silver",               backFillColor: "gold",               backFontColor: "red",               backFontSize: 24,               msg: "谢谢惠顾"           };           for (var p in  desAttr)           {               defaultAttr[p] = desAttr[p];           }              return defaultAttr;          },             init: function (desAttr)       {              var attr = this.mergeAttr(desAttr);              //初始化canvas           this.backCanvas.penColor(attr.backFillColor);           this.backCanvas.fontSize(attr.backFontSize);           this.backCanvas.drawRect({x: 0, y: 0}, {x: this.backCanvas.width(), y: this.backCanvas.height()}, true);           this.backCanvas.penColor(attr.backFontColor);           this.backCanvas.drawTextInCenter(attr.msg, true);           //初始化canvas           this.frontCanvas.penColor(attr.frontFillColor);           this.frontCanvas.drawRect({x: 0, y: 0}, {x: this.frontCanvas.width(), y: this.frontCanvas.height()}, true);              var _this = this;           //设置事件           this.$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参数，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，测试一下：

基本实现了刮开图层，但是存在一个小问题，就是当用户滑动特别快时，会出现一些断点，当然也可以忽略，不过我们准备提供一下解决方案：

产生原因：由于鼠标移动速度过快，产生的断点；解决方案：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，根据斜率，然后分成多个小段，分别获得线段上的坐标（有四种可能，有兴趣可以画画图，计算下，代码如下）：

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.$eleBack);          this.isStart = false;      }      GuaGuaLe.prototype = {       constructor: GuaGuaLe,       /**       * 将用户的传入的参数和默认参数做合并       * @param desAttr       * @returns {{frontFillColor: string, backFillColor: string, backFontColor: string, backFontSize: number, msg: string}}       */       mergeAttr: function (desAttr)       {           var defaultAttr = {               frontFillColor: "silver",               backFillColor: "gold",               backFontColor: "red",               backFontSize: 24,               msg: "谢谢惠顾"           };           for (var p in  desAttr)           {               defaultAttr[p] = desAttr[p];           }              return defaultAttr;          },             init: function (desAttr)       {              var attr = this.mergeAttr(desAttr);              //初始化canvas           this.backCanvas.penColor(attr.backFillColor);           this.backCanvas.fontSize(attr.backFontSize);           this.backCanvas.drawRect({x: 0, y: 0}, {x: this.backCanvas.width(), y: this.backCanvas.height()}, true);           this.backCanvas.penColor(attr.backFontColor);           this.backCanvas.drawTextInCenter(attr.msg, true);           //初始化canvas           this.frontCanvas.penColor(attr.frontFillColor);           this.frontCanvas.drawRect({x: 0, y: 0}, {x: this.frontCanvas.width(), y: this.frontCanvas.height()}, true);              var _this = this;           //设置事件           this.$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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canvas 模拟实现电子彩票刮刮乐的代码

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