canvas大转盘抽奖
一、代码
1.html 部分
<body style="background:#e62d2d;overflow-x:hidden;">
<img src="images/1.png" id="shan-img" style="display:none;" />
<img src="images/2.png" id="sorry-img" style="display:none;" />
<div class="banner">
<div class="turnplate" style="background-image:url(images/turnplate-bg.png);background-size:100% 100%;">
<canvas class="item" id="wheelcanvas" width="422px" height="422px"></canvas>
<img class="pointer" src="images/turnplate-pointer.png"/>
</div>
</div>
</body>2.js部分
<script type="text/javascript">
var turnplate={
restaraunts:[], //大转盘奖品名称
colors:[], //大转盘奖品区块对应背景颜色
outsideRadius:192, //大转盘外圆的半径
textRadius:155, //大转盘奖品位置距离圆心的距离
insideRadius:68, //大转盘内圆的半径
startAngle:0, //开始角度
bRotate:false //false:停止;ture:旋转
};
$(document).ready(function(){
//动态添加大转盘的奖品与奖品区域背景颜色
turnplate.restaraunts = ["50M免费流量包", "10闪币", "谢谢参与", "5闪币", "10M免费流量包", "20M免费流量包", "20闪币 ", "30M免费流量包", "100M免费流量包", "2闪币"];
turnplate.colors = ["#FFF4D6", "#FFFFFF", "#FFF4D6", "#FFFFFF","#FFF4D6", "#FFFFFF", "#FFF4D6", "#FFFFFF","#FFF4D6", "#FFFFFF"];
var rotateTimeOut = function (){
$('#wheelcanvas').rotate({
angle:0,
animateTo:2160,
duration:8000,
callback:function (){
alert('网络超时，请检查您的网络设置！');
}
});
};
//旋转转盘 item:奖品位置; txt：提示语;
var rotateFn = function (item, txt){
var angles = item * (360 / turnplate.restaraunts.length) - (360 / (turnplate.restaraunts.length*2));
// 旋转角度 == 270°（当前第一个角度和指针位置的偏移量）
if(angles<270){
angles = 270 - angles;
}else{
angles = 360 - angles + 270;
}
$('#wheelcanvas').stopRotate();
$('#wheelcanvas').rotate({
angle:0,
animateTo:angles+1800,
duration:8000,
callback:function (){
alert(txt);
turnplate.bRotate = !turnplate.bRotate;
}
});
};
// 指针点击
$('.pointer').click(function (){
if(turnplate.bRotate)return;
turnplate.bRotate = !turnplate.bRotate;
//获取随机数(奖品个数范围内)
var item = rnd(1,turnplate.restaraunts.length);
//奖品数量等于10,指针落在对应奖品区域的中心角度[252, 216, 180, 144, 108, 72, 36, 360, 324, 288]
rotateFn(item, turnplate.restaraunts[item-1]);
/* switch (item) {
case 1:
rotateFn(252, turnplate.restaraunts[0]);
break;
case 2:
rotateFn(216, turnplate.restaraunts[1]);
break;
case 3:
rotateFn(180, turnplate.restaraunts[2]);
break;
case 4:
rotateFn(144, turnplate.restaraunts[3]);
break;
case 5:
rotateFn(108, turnplate.restaraunts[4]);
break;
case 6:
rotateFn(72, turnplate.restaraunts[5]);
break;
case 7:
rotateFn(36, turnplate.restaraunts[6]);
break;
case 8:
rotateFn(360, turnplate.restaraunts[7]);
break;
case 9:
rotateFn(324, turnplate.restaraunts[8]);
break;
case 10:
rotateFn(288, turnplate.restaraunts[9]);
break;
} */
console.log(item);
});
});
// 随机函数
function rnd(n, m){
var random = Math.floor(Math.random()*(m-n+1)+n);
return random;
}
//页面所有元素加载完毕后执行drawRouletteWheel()方法对转盘进行渲染
window.onload=function(){
drawRouletteWheel();
};
// 画布
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 = "#FFBE04";
//font 属性设置或返回画布上文本内容的当前字体属性
ctx.font = '16px Microsoft YaHei';
for(var i = 0; i < turnplate.restaraunts.length; i++) {
var angle = turnplate.startAngle + i * arc;
ctx.fillStyle = turnplate.colors[i];
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）
ctx.arc(211, 211, turnplate.outsideRadius, angle, angle + arc, false);
ctx.arc(211, 211, 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----
ctx.fillStyle = "#E5302F";
var text = turnplate.restaraunts[i];
var line_height = 17;
//translate方法重新映射画布上的 (0,0) 位置
ctx.translate(211 + Math.cos(angle + arc / 2) * turnplate.textRadius, 211 + 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);
/** 下面代码根据奖品类型、奖品名称长度渲染不同效果，如字体、颜色、图片效果。(具体根据实际情况改变) **/
if(text.indexOf("M")>0){//流量包
var texts = text.split("M");
for(var j = 0; j<texts.length; j++){
ctx.font = j == 0?'bold 20px Microsoft YaHei':'16px Microsoft YaHei';
if(j == 0){
ctx.fillText(texts[j]+"M", -ctx.measureText(texts[j]+"M").width / 2, j * line_height);
}else{
ctx.fillText(texts[j], -ctx.measureText(texts[j]).width / 2, j * line_height);
}
}
}else if(text.indexOf("M") == -1 && text.length>6){//奖品名称长度超过一定范围
text = text.substring(0,6)+"||"+text.substring(6);
var texts = text.split("||");
for(var j = 0; j<texts.length; j++){
ctx.fillText(texts[j], -ctx.measureText(texts[j]).width / 2, j * line_height);
}
}else{
//在画布上绘制填色的文本。文本的默认颜色是黑色
//measureText()方法返回包含一个对象，该对象包含以像素计的指定字体宽度
ctx.fillText(text, -ctx.measureText(text).width / 2, 0);
}
//添加对应图标
if(text.indexOf("闪币")>0){
var img= document.getElementById("shan-img");
img.onload=function(){
ctx.drawImage(img,-15,10);
};
ctx.drawImage(img,-15,10);
}else if(text.indexOf("谢谢参与")>=0){
var img= document.getElementById("sorry-img");
img.onload=function(){
ctx.drawImage(img,-15,10);
};
ctx.drawImage(img,-15,10);
}
//把当前画布返回（调整）到上一个save()状态之前
ctx.restore();
//----绘制奖品结束----
}
}
}
</script>3.css部分
body,ul,ol,li,p,h1,h2,h3,h4,h5,h6,form,fieldset,table,td,img,div{margin:0;padding:0;border:0;}
body{color:#333; font-size:12px;font-family:"Microsoft YaHei"}
ul,ol{list-style-type:none;}
select,input,img,select{vertical-align:middle;}
input{ font-size:12px;}
a{ text-decoration:none; color:#000;}
a:hover{color:#c00; text-decoration:none;}
.clear{clear:both;}
/* 大转盘样式 */
.banner{display:block;width:95%;margin-left:auto;margin-right:auto;margin-bottom: 20px;}
.banner .turnplate{display:block;width:100%;position:relative;}
.banner .turnplate canvas.item{width:100%;}
.banner .turnplate img.pointer{position:absolute;width:31.5%;height:42.5%;left:34.6%;top:23%;}二、效果预览
github地址：https://github.com/zylgt/h5-
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