標籤：html5 css3 canvas 刮刮樂
轉載請標明出處：http://blog.csdn.net/lmj623565791/article/details/34089553
今天給大家帶來一個刮刮樂的小例子~基於HTML5 canvas的，有興趣的可以改成android版本的，或者其他的~
：
貼一張我中500w的照片，咋辦啊，怎麼花呢~
好了，下面開始原理：
1、刮獎地區兩個Canvas，一個是front ， 一個back ，front遮蓋住下面的canvas。
2、canvas預設填充了一個矩形，將下面canvas遮蓋，然後監聽mouse事件，根據mousemove的x,y座標，進行擦出front canvas上的矩形地區，然後顯示出下面的canvas的。
很簡單把~嘿嘿~
1、HTML檔案內容：
<!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"> $(function () { var guaguale = new GuaGuaLe("front", "back"); guaguale.init({msg: "￥5000000.00"}); }); </script> <style type="text/css"> body { background: url("s_bd.jpg") repeat 0 0; } .container { position: relative; width: 400px; height: 160px; margin: 100px auto 0; background: url(s_title.png) no-repeat 0 0; background-size: 100% 100%; } #front, #back { position: absolute; width: 200px; left: 50%; top: 100%; margin-left: -130px; height: 80px; border-radius: 5px; border: 1px solid #444; } </style></head><body><div class="container"> <canvas id="back" width="200" height="80"></canvas> <canvas id="front" width="200" height="80"></canvas></div></body></html>
2、首先我利用了一個以前寫的canvas輔助類，留下來今天要用的一些方法：
/** * Created with JetBrains WebStorm. * User: zhy * Date: 13-12-17 * Time: 下午9:42 * To change this template use File | Settings | File Templates. */function Canvas2D($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"; /** * 繪製矩形 * @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); } }; /** * 根據書寫的文本，得到該文本在canvas上書寫的中心位置的左上方座標 * @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(); } /** * 當螢幕大小發生變化，重新計算offset */ $(window).resize(function () { pageOffset = $canvas.offset(); }); /** * 將頁面上的左邊轉化為canvas中的座標 * @param pageX * @param pageY * @returns {{x: number, y: number}} */ this.getCanvasPoint = function (pageX, pageY) { return{ x: pageX - pageOffset.left, y: pageY - pageOffset.top } } /** * 清除地區，此使用者滑鼠擦出刮獎塗層 * @param start * @returns {*} */ this.clearRect = function (start) { context.clearRect(start.x, start.y, 10, 10); return this; }; /** *將文本繪製到canvas的中間 * @param text * @param fill */ this.drawTextInCenter = function (text, fill) { var point = this.caculateTextCenterPos(text); if (fill) { context.fillText(text, point.x, point.y); } else { context.strokeText(text, point.x, point.y); } }; /** * 設定畫筆寬度 * @param newWidth * @returns {*} */ this.penWidth = function (newWidth) { if (arguments.length) { context.lineWidth = newWidth; return this; } return context.lineWidth; }; /** * 設定畫筆顏色 * @param newColor * @returns {*} */ this.penColor = function (newColor) { if (arguments.length) { context.strokeStyle = newColor; context.fillStyle = newColor; return this; } return context.strokeStyle; }; /** * 設定字型大小 * @param fontSize * @returns {*} */ this.fontSize = function (fontSize) { if (arguments.length) { context.font = fontSize + "px Verdana, Geneva, sans-serif"; return this; } return context.fontSize; }}
3、GuaGuaLe.js
/** * Created with JetBrains WebStorm. * User: zhy * Date: 14-6-24 * Time: 上午11:36 * To change this template use File | Settings | File Templates. */function GuaGuaLe(idFront, idBack){ this.$eleBack = $("#" + idBack); this.$eleFront = $("#" + idFront); this.frontCanvas = new Canvas2D(this.$eleFront); this.backCanvas = new Canvas2D(this.$eleBack); this.isStart = false;}GuaGuaLe.prototype = { constructor: GuaGuaLe, /** * 將使用者的傳入的參數和預設參數做合并 * @param desAttr * @returns {{frontFillColor: string, backFillColor: string, backFontColor: string, backFontSize: number, msg: string}} */ mergeAttr: function (desAttr) { var defaultAttr = { frontFillColor: "silver", backFillColor: "gold", backFontColor: "red", backFontSize: 24, msg: "謝謝惠顧" }; for (var p in desAttr) { defaultAttr[p] = desAttr[p]; } return defaultAttr; }, init: function (desAttr) { var attr = this.mergeAttr(desAttr); //初始化canvas this.backCanvas.penColor(attr.backFillColor); this.backCanvas.fontSize(attr.backFontSize); this.backCanvas.drawRect({x: 0, y: 0}, {x: this.backCanvas.width(), y: this.backCanvas.height()}, true); this.backCanvas.penColor(attr.backFontColor); this.backCanvas.drawTextInCenter(attr.msg, true); //初始化canvas this.frontCanvas.penColor(attr.frontFillColor); this.frontCanvas.drawRect({x: 0, y: 0}, {x: this.frontCanvas.width(), y: this.frontCanvas.height()}, true); var _this = this; //設定事件 this.$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; }};
好了，然後就基本完工了，測試一下：
基本實現了刮開圖層，但是存在一個小問題，就是當使用者滑動特別快時，會出現一些斷點，當然也可以忽略，不過我們準備提供一下解決方案：
產生原因：由於滑鼠移動速度過快，產生的斷點；解決方案：將mousemove中兩次的滑鼠左邊，進行拆分成多個斷點座標：
如，把兩點之間進行連線，根據斜率，然後分成多個小段，分別獲得線段上的座標（有四種可能，有興趣可以畫畫圖，計算下，代碼如下）：
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;
/** * 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.$eleBack); this.isStart = false;}GuaGuaLe.prototype = { constructor: GuaGuaLe, /** * 將使用者的傳入的參數和預設參數做合并 * @param desAttr * @returns {{frontFillColor: string, backFillColor: string, backFontColor: string, backFontSize: number, msg: string}} */ mergeAttr: function (desAttr) { var defaultAttr = { frontFillColor: "silver", backFillColor: "gold", backFontColor: "red", backFontSize: 24, msg: "謝謝惠顧" }; for (var p in desAttr) { defaultAttr[p] = desAttr[p]; } return defaultAttr; }, init: function (desAttr) { var attr = this.mergeAttr(desAttr); //初始化canvas this.backCanvas.penColor(attr.backFillColor); this.backCanvas.fontSize(attr.backFontSize); this.backCanvas.drawRect({x: 0, y: 0}, {x: this.backCanvas.width(), y: this.backCanvas.height()}, true); this.backCanvas.penColor(attr.backFontColor); this.backCanvas.drawTextInCenter(attr.msg, true); //初始化canvas this.frontCanvas.penColor(attr.frontFillColor); this.frontCanvas.drawRect({x: 0, y: 0}, {x: this.frontCanvas.width(), y: this.frontCanvas.height()}, true); var _this = this; //設定事件 this.$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; }};
好了，收工吃飯~
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