javascrip+HTML5 Canvas绘制转盘抽奖_javascript技巧

.lunck_draw_wrap{display:block;width:95%;margin-right:auto;}
 .lunck_draw_wrap .turnplate{display:block;width:106%; position:relative;}
  .lunck_draw_wrap .turnplate canvas.item{left:1px;
  position: relative;
  top:9px;
  width:100%;}
  .lunck_draw_wrap .turnplate img.pointer{ height:37.5%;
  left:34.6%;
  position: absolute;
  top:30%;
  width:31.5%;}

var turnplate ={
 restaraunts:[],//大转盘奖品名称
 lucky:[],//奖品内容
 colors:[],//大转盘奖品区块对应背景颜色
 goodsimgArr:[],//奖品图片页面标签
 outsideRadius:175,//大转盘外圆的半径
 textRadius:140,//大转盘奖品位置距离圆心的距离
 insideRadius:65,//大转盘内圆的半径
 startAngle:0,//开始角度
 bRotate:false//false:停止;ture:旋转
 };

$.each(data.list,function(key, value){
 turnplate.restaraunts.push(value.data0);
 turnplate.lucky.push(value.data1);
 turnplate.goodsimgArr.push(getLuckyImg + value.data4);
 if(key %2==0)
 turnplate.colors.push("#fff");
 else
 turnplate.colors.push("#5fcbd4");
 })
 

[
 {
 "data0":"一等奖",
 "data1":"iphone6s",
 "data2":"0",
 "data3":"0",
 "data4":"201510161406303384.png",
 "data5":"XXXX网络科技",
 "data6":"浙江省衢州市柯城区XXXXX",
 "data7":"0570-XXXXXX"
 },......
 ]

turnplate.goodsimgArr.push('../images/hongbao.png')
 turnplate.restaraunts.push("优胜奖");
 turnplate.colors.push("#5fcbd4");
 //页面所有元素加载完毕后执行drawRouletteWheel()方法对转盘进行渲染
 preloadimages(turnplate.goodsimgArr).done(function(images){
 drawRouletteWheel();
 });

//对奖品图片预加载
 function preloadimages(arr){
 var newimages =[], loadedimages =0
 var postaction =function(){}//此处增加了一个postaction函数
 var arr =(typeof arr !="object")?[arr]: arr
 function imageloadpost(){
 loadedimages++
 if(loadedimages == arr.length){
 postaction(newimages)//加载完成用我们调用postaction函数并将newimages数组做为参数传递进去
 }
 }
 for(var i =0; i < arr.length; i++){
 newimages[i]=newImage()
 newimages[i].src = arr[i]
 newimages[i].onload =function(){
 imageloadpost()
 }
 newimages[i].onerror =function(){
 imageloadpost()
 }
 }
 return{//此处返回一个空白对象的done方法
 done:function(f){
 postaction = f || postaction
 }
 }
 }

function drawRouletteWheel(){
 var canvas = document.getElementById("wheelcanvas");
 if(canvas.getContext){
 //根据奖品个数计算圆周角度
 var arc =Math.PI /(turnplate.restaraunts.length /2);
 var ctx = canvas.getContext("2d");
 //在给定矩形内清空一个矩形
 ctx.clearRect(0,0,422,422);
 //strokeStyle 属性设置或返回用于笔触的颜色、渐变或模式
 ctx.strokeStyle ="rgba(0,0,0,0)";
 //font 属性设置或返回画布上文本内容的当前字体属性
 ctx.font ='bold 18px Microsoft YaHei';
 for(var i =0; i < turnplate.restaraunts.length; i++){
 //根据当前奖品索引 计算绘制的扇形开始弧度
 var angle = turnplate.startAngle + i * arc;
 //根据奖品参数 绘制扇形填充颜色
 ctx.fillStyle = turnplate.colors[i];
 //开始绘制扇形
 ctx.beginPath();
 //arc(x,y,r,起始角,结束角,绘制方向) 方法创建弧/曲线（用于创建圆或部分圆）
 //绘制大圆
 ctx.arc(212,212, turnplate.outsideRadius, angle, angle + arc,false);
 //绘制小圆
 ctx.arc(212,212, turnplate.insideRadius, angle + arc, angle,true);
 ctx.stroke();
 ctx.fill();
 //锁画布(为了保存之前的画布状态)
 ctx.save();
 //----绘制奖品开始----
 //奖品默认字体颜色
 ctx.fillStyle ="#fff";
 var text = turnplate.restaraunts[i];
 var lukyname = turnplate.lucky[i];
 var line_height =17;
 //translate方法重新映射画布上的 (0,0) 位置
 ctx.translate(212+Math.cos(angle + arc /2)* turnplate.textRadius,212+Math.sin(angle + arc /2)* turnplate.textRadius);
 //rotate方法旋转当前的绘图
 ctx.rotate(angle + arc /2+Math.PI /2);
 //绘制奖品图片
 var img =newImage();
 img.src = turnplate.goodsimgArr[i];
 ctx.drawImage(img,-17,35);
 //由于设计的转盘色块是交错的，所以这样可以实现相邻奖品区域字体颜色不同
 if(i %2==0){
 ctx.fillStyle ="#f7452f";
 }
 //将字体绘制在对应坐标
 ctx.fillText(text,-ctx.measureText(text).width /2,0);
 //设置字体
 ctx.font =' 14px Microsoft YaHei';
 //绘制奖品名称
 if(text !="优胜奖"){
 ctx.fillText(lukyname,-ctx.measureText(lukyname).width /2,25);
 }else{
 ctx.fillText("优麦币",-ctx.measureText("优麦币").width /2,25);
 }
 //把当前画布返回（插入）到上一个save()状态之前
 ctx.restore();
 ctx.save();
 //----绘制奖品结束----
 }
 }
 }

<divclass="lunck_draw_wrap">
 <divclass="turnplate"style=" background-size:100%100%;">
 <canvasclass="item"id="wheelcanvas"width="422px"height="422px"></canvas>
 <img class="pointer"  style="max-width:90%"src="../images/chouzhang12.png"/ alt="javascrip+HTML5 Canvas绘制转盘抽奖_javascript技巧" >
 <img class="pointer"src="../images/hianji .png"/ alt="javascrip+HTML5 Canvas绘制转盘抽奖_javascript技巧" >
 </div>
 </div>

$('.lunck_draw_wrap').delegate("img.pointer","click",function(){
 if(turnplate.bRotate)return;
 turnplate.bRotate =!turnplate.bRotate;
 $.getJSON("../AJAX/lottery.ashx","",function(data){
 //1090系统配置错误，1091用户未登陆或用户数据异常，1092用户剩余积分不足,1093未中奖
 hideInput("code",data.code)
 if(data.code.toString()=="1090"){
 iosalert("系统配置错误")
 }elseif(data.code.toString()=="1091"){
 iosalert("用户未登陆或用户数据异常")
 }elseif(data.code.toString()=="1092"){
 iosalert("用户剩余积分不足")
 }elseif(data.code.toString()=="1094"){
 iosalert("超过每日抽奖次数")
 }
 else{
 var upoint =0;
 upoint = parseInt($("#uPoint").html())- parseInt($("#sPoint").html());
 $("#uPoint").html(upoint);
 if(data.isWin =='true'){
 item = getArrayIndex(turnplate.restaraunts, data.name);
 rotateFn(item +1,"恭喜获得，"+ turnplate.restaraunts[item]);
 }
 else{
 rotateFn(0,"恭喜获得优胜奖！");
 }
 }
 })
 });

//旋转转盘 item:奖品位置; txt：提示语;
 var rotateFn =function(item, txt){
 //根据传进来的奖品序号 计算相应的弧度
 var angles = item *(360/ turnplate.restaraunts.length)-(360/(turnplate.restaraunts.length *2));
 if(angles <270){
 angles =270- angles;
 }else{
 angles =360- angles +270;
 }
 //强制停止转盘的转动
 $('#wheelcanvas').stopRotate();
 //调用转动方法，设置转动所需参数和回调函数
 $('#wheelcanvas').rotate({
 //起始角度
 angle:0,
 //转动角度 +1800是为了多转几圈
 animateTo: angles +1800,
 duration:8000,
 callback:function(){
 iosSuccess(txt);
 turnplate.bRotate =!turnplate.bRotate;
 if($("#code").val()!="1093"){
 delayLoad(getHttpPrefix +"graphicdetails.html&#63;lukyid="+ $("#code").val())
 }
 }
 });
 };