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   源码介绍

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Lottery
一个刮奖小程序，可以在移动设备上和PC端网页（浏览器要支持canvas）上运行


function Lottery(id, cover, coverType, width, height, drawPercentCallback) { this.conId = id; this.conNode = document.getElementById(this.conId); this.cover = cover; this.coverType = coverType; this.background = null; this.backCtx = null; this.mask = null; this.maskCtx = null; this.lottery = null; this.lotteryType = 'image'; this.width = width || 300; this.height = height || 100; this.clientRect = null; this.drawPercentCallback = drawPercentCallback; } Lottery.prototype = { createElement: function (tagName, attributes) { var ele = document.createElement(tagName); for (var key in attributes) { ele.setAttribute(key, attributes[key]); } return ele; }, getTransparentPercent: function(ctx, width, height) { var imgData = ctx.getImageData(0, 0, width, height), pixles = imgData.data, transPixs = []; for (var i = 0, j = pixles.length; i < j; i = 4) { var a = pixles[i 3]; if (a < 128) { transPixs.push(i); } } return (transPixs.length / (pixles.length / 4) * 100).toFixed(2); }, resizeCanvas: function (canvas, width, height) { canvas.width = width; canvas.height = height; canvas.getContext('2d').clearRect(0, 0, width, height); }, drawPoint: function (x, y) { this.maskCtx.beginPath(); var radgrad = this.maskCtx.createRadialGradient(x, y, 0, x, y, 30); radgrad.addColorStop(0, 'rgba(0,0,0,0.6)'); radgrad.addColorStop(1, 'rgba(255, 255, 255, 0)'); this.maskCtx.fillStyle = radgrad; this.maskCtx.arc(x, y, 30, 0, Math.PI * 2, true); this.maskCtx.fill(); if (this.drawPercentCallback) { this.drawPercentCallback.call(null, this.getTransparentPercent(this.maskCtx, this.width, this.height)); } }, bindEvent: function () { var _this = this; var device = (/android|webos|iphone|ipad|ipod|blackberry|iemobile|opera mini/i.test(navigator.userAgent.toLowerCase())); var clickEvtName = device ? 'touchstart' : 'mousedown'; var moveEvtName = device? 'touchmove': 'mousemove'; if (!device) { var isMouseDown = false; document.addEventListener('mouseup', function(e) { isMouseDown = false; }, false); } else { document.addEventListener("touchmove", function(e) { if (isMouseDown) { e.preventDefault(); } }, false); document.addEventListener('touchend', function(e) { isMouseDown = false; }, false); } this.mask.addEventListener(clickEvtName, function (e) { isMouseDown = true; var docEle = document.documentElement; if (!_this.clientRect) { _this.clientRect = { left: 0, top:0 }; } var x = (device ? e.touches[0].clientX : e.clientX) - _this.clientRect.left docEle.scrollLeft - docEle.clientLeft; var y = (device ? e.touches[0].clientY : e.clientY) - _this.clientRect.top docEle.scrollTop - docEle.clientTop; _this.drawPoint(x, y); }, false); this.mask.addEventListener(moveEvtName, function (e) { if (!device && !isMouseDown) { return false; } var docEle = document.documentElement; if (!_this.clientRect) { _this.clientRect = { left: 0, top:0 }; } var x = (device ? e.touches[0].clientX : e.clientX) - _this.clientRect.left docEle.scrollLeft - docEle.clientLeft; var y = (device ? e.touches[0].clientY : e.clientY) - _this.clientRect.top docEle.scrollTop - docEle.clientTop; _this.drawPoint(x, y); }, false); }, drawLottery: function () { this.background = this.background || this.createElement('canvas', { style: 'position:absolute;left:0;top:0;' }); this.mask = this.mask || this.createElement('canvas', { style: 'position:absolute;left:0;top:0;' }); if (!this.conNode.innerHTML.replace(/[\w\W]| /g, '')) { this.conNode.appendChild(this.background); this.conNode.appendChild(this.mask); this.clientRect = this.conNode ? this.conNode.getBoundingClientRect() : null; this.bindEvent(); } this.backCtx = this.backCtx || this.background.getContext('2d'); this.maskCtx = this.maskCtx || this.mask.getContext('2d'); if (this.lotteryType == 'image') { var image = new Image(), _this = this; image.onload = function () { _this.width = this.width; _this.height = this.height; _this.resizeCanvas(_this.background, this.width, this.height); _this.backCtx.drawImage(this, 0, 0); _this.drawMask(); } image.src = this.lottery; } else if (this.lotteryType == 'text') { this.width = this.width; this.height = this.height; this.resizeCanvas(this.background, this.width, this.height); this.backCtx.save(); this.backCtx.fillStyle = '#FFF'; this.backCtx.fillRect(0, 0, this.width, this.height); this.backCtx.restore(); this.backCtx.save(); var fontSize = 30; this.backCtx.font = 'Bold ' fontSize 'px Arial'; this.backCtx.textAlign = 'center'; this.backCtx.fillStyle = '#F60'; this.backCtx.fillText(this.lottery, this.width / 2, this.height / 2 fontSize / 2); this.backCtx.restore(); this.drawMask(); } }, drawMask: function() { this.resizeCanvas(this.mask, this.width, this.height); if (this.coverType == 'color') { this.maskCtx.fillStyle = this.cover; this.maskCtx.fillRect(0, 0, this.width, this.height); this.maskCtx.globalCompositeOperation = 'destination-out'; } else if (this.coverType == 'image'){ var image = new Image(), _this = this; image.onload = function () { _this.maskCtx.drawImage(this, 0, 0); _this.maskCtx.globalCompositeOperation = 'destination-out'; } image.src = this.cover; } }, init: function (lottery, lotteryType) { this.lottery = lottery; this.lotteryType = lotteryType || 'image'; this.drawLottery(); } }