uniapp小程序刮刮乐抽奖

使用canvas画布画出刮刮乐要被刮的图片，使用移动清除画布。

当前代码封装为刮刮乐的组件；

vue代码：

<template>
	<view class="page" v-if="merchantInfo.cdn_static">
		<image class="bg" :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/page_bg.png'" mode="aspectFill"></image>
		<view class="content">
			<view class="logo">
				<image :src="merchantInfo.logo" mode="heightFix"></image>
			</view>
			<view class="title">
				<image :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/title.png'" mode="heightFix"></image>
			</view>
			<view class="notification">
				<view></view>
				<text>每日刮卡抽好礼</text>
				<view></view>
			</view>
			<view class="box">
				<image class="scrapingBg" :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/scrapingBg.png'"></image>
				<view class="scrapingBox">
					<view class="scrapingBoxContent">
						<!-- 奖品名称 -->
						<!-- <view>{{ prizeTitle || "" }}</view> -->
						<!-- 奖品图片 -->
						<image :src="merchantInfo.cdn_static + prizeUrl"></image>
						<canvas :style="{'width':width+'px','height':height+'px'}" style="position: absolute; top: 0;" canvas-id="myCanvas" id="myCanvas" @touchstart="touchstart" @touchend="touchend" @touchmove="touchmove"></canvas>
					</view>
				</view>
			</view>
			<view class="count">
				<view class="tip">您今天还有<text>{{total}}</text>次抽奖机会</view>
			</view>
			<view class="btns">
				<view class="btn" @click="getRule">
					<image class="btnImg" :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/rule.png'"></image>
					<view class="btnConent">
						<image :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/ruleIcon.png'"></image>
						<text>查看规则</text>
					</view>
				</view>
				<view class="btn" @click="getResult()">
					<image class="btnImg" :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/prize.png'"></image>
					<view class="btnConent">
						<image :src="merchantInfo.cdn_static +'statistics/luckDrawImg/scratchcard/prizeIcon.png'"></image>
						<text>兑换福利</text>
					</view>
				</view>
			</view>
		</view>
		<view class="win" v-if="rule_show">
			<scroll-view scroll-y class="win_box .win_box_bg">
				<mp-html :content="luckDrawInfo.rule" />
			</scroll-view>
			<text class="iconfont iconcolseIcon theme-font-white" @click="rule_show=false"></text>
		</view>
		<view class="win" v-if="result_show">
			<view class="win_box1">
				<image class="win_bg" :src="merchantInfo.cdn_static +'statistics/luckDrawImg/result_bg.png'" mode=""></image>
				<view class="win_content">
					<view class="win_tips theme-font-white">{{currentPrize.desc}}</view>
					<view class="win_title">{{currentPrize.title}}</view>
					<view class="win_btn" @click="choiseAddress()">{{currentPrize.is_address==1?'选择地址':'确定'}}</view>
				</view>
			</view>
		</view>
		<view class="win" v-if="prize_show">
			<view class="win_tit theme-font-white">我的奖品</view>
			<view class="win_box2">
				<view class="items">
					<view class="left i_title">奖品</view>
					<view class="right i_title">中奖时间</view>
				</view>
				<scroll-view scroll-y class="list">
					<view class="item" v-for="(item,index) in list" :key="index">
						<view class="left">{{item.lottery_prize_title}}</view>
						<view class="right" v-if="item.is_address==1&&!item.address_id">
							<view class="r_btn"  @click="choiseAddress1(item)">去领奖</view>
						</view>
						<view class="right" v-else>{{item.created_time}}</view>
					</view>
				</scroll-view>
			</view>
			<text class="iconfont iconcolseIcon theme-font-white" @click="prize_show=false"></text>
		</view>
	</view>

</template>

<script>
	import { luckDrawInfo } from '@/api/luckDraw.js';
	import colors from '@/mixins/color';
	export default {
		mixins: [colors],
		data() {
			return {//https://cdn.dev.scrm.juplus.cn/InQLzDLoAl2S9LyNJUXQ45gpA.png
				mask: true,
				wtf:true,
				luckDrawInfo: {},
				rule_show:false,
				result_show:false,
				prize_show:false,
				total:0,
				currentPrize:{},
				list:[],
				id: "",
				prizeTitle: "",
				prizeUrl: "",
				filePath: "",
				ctx: null,
				width: 0,
				height: 0,
				disabled: false, // 是否禁止刮卡
				readyState: false, // 是否开始绘制
				endState: false, // 结束刮卡状态
				watermark: '刮一刮', // 水印文字
				watermarkColor: '#c5c5c5', // 水印文字颜色
				watermarkSize: 14, // 水印文字大小
				title: '刮一刮开奖', // 提示文字
				titleColor: '#888', // 提示文字颜色
				titleSize: 24, // 提示文字大小
				startX: 0, // 触摸x轴位置
				startY: 0, // 触摸y轴位置
				touchSize: 30, // 触摸画笔大小
				percentage: 50, // 刮开百分之多少的时候开奖
			}
		},
		props: {
			userId: {
				type: [Number,String]
			},
			type:{
				type: [Number,String]
			}
		},
		//渲染完了
		mounted() {
			this.id = this.userId;
			this.init();
			this.$nextTick(() => {
				let content = uni.createSelectorQuery().in(this).select(".scrapingBoxContent");
				content.boundingClientRect((data) => {
					this.width = data.width;
					this.height = data.height;
					this.ctx = uni.createCanvasContext('myCanvas', this);
					uni.getImageInfo({
						src: this.merchantInfo.cdn_static + 'statistics/luckDrawImg/scratchcard/scratchingBefore.png',
						success: (res) => {
							this.filePath = res.path;
							this.drawInit();
						}
					})
				}).exec()
			})
		},	
		methods: {
			drawInit(imgUrl) {
				this.endState = false;
				this.readyState = false;
				this.ctx.clearRect(0, 0, this.width, this.height); // 清除画布上在该矩形区域内的内容(x,y,宽，高)。
				// this.ctx.setFillStyle('#ddd'); // 填充颜色
				// this.ctx.fillRect(0, 0, this.width, this.height); // 填充区域（x,y,宽,高）
				/**
				 * 绘制文字水印
				 */
				// var width = this.watermark.length * this.watermarkSize;
				// this.ctx.save(); // 保存当前的绘图上下文。
				// this.ctx.rotate(-10 * Math.PI / 180); // 以原点为中心，原点可以用 translate方法修改。顺时针旋转当前坐标轴。多次调用rotate，旋转的角度会叠加。
				// let x = 0;
				// let y = 0;
				// let i = 0;
				// while ((x <= this.width * 5 || y <= this.height * 5) && i < 300) {
				// 	this.ctx.setFillStyle(this.watermarkColor); // 填充颜色
				// 	this.ctx.setFontSize(this.watermarkSize); // 设置字体的字号
				// 	this.ctx.fillText(this.watermark, x, y); // 填充的文本（文字，x，y）
				// 	x += width + width * 1.6;
				// 	if (x > this.width && y <= this.height) {
				// 		x = -Math.random() * 100;
				// 		y += this.watermarkSize * 3;
				// 	}
				// 	i++;
				// }
				// this.ctx.restore(); // 恢复之前保存的绘图上下文。
				/**
				 * 绘制标题
				 */
				// this.ctx.setTextAlign("center"); // 用于设置文字的对齐
				// this.ctx.setTextBaseline("middle"); // 用于设置文字的水平对齐
				// this.ctx.setFillStyle(this.titleColor); // 填充颜色
				// this.ctx.setFontSize(this.titleSize); // 设置字体的字号
				// this.ctx.fillText(this.title, this.width / 2, this.height / 2); // 填充的文本（文字，x，y）
				
				/**
				 * 绘制图片
				 */ 
				this.ctx.drawImage(this.filePath, 0, 0, this.width, this.height); 

				this.ctx.draw(); // 将之前在绘图上下文中的描述（路径、变形、样式）画到 canvas 中。
				this.readyState = true; // 完成绘制
			},
			// 手指触摸动作开始
			touchstart(e) {
				if (this.disabled || this.endState) {
					return;
				}
				this.startPlay();
				this.startX = e.touches[0].x;
				this.startY = e.touches[0].y;
			},
			// 手指触摸后移动
			touchmove(e) {
				if (this.disabled || this.endState) return;
				if (!this.prizeTitle) return;
				if (!this.prizeUrl) return;
				this.ctx.clearRect(this.startX, this.startY, this.touchSize, this.touchSize); // 清除画布上在该矩形区域内的内容(x,y,宽，高)。
				this.ctx.draw(true); // false:本次绘制是否接着上一次绘制，true:保留当前画布上的内容
				//记录移动点位
				this.startX = e.touches[0].x;
				this.startY = e.touches[0].y;
			},
			// 手指触摸动作结束
			touchend(e) {
				if (this.disabled || this.endState) {
					return;
				}
				// 返回一个数组，用来描述 canvas 区域隐含的像素数据，在自定义组件下，第二个参数传入自定义组件实例 this，以操作组件内 <canvas> 组件。
				uni.canvasGetImageData({
					canvasId: 'myCanvas',
					x: 0,
					y: 0,
					width: this.width,
					height: this.height,
					success: (res) => {
						console.log(res);
						let pixels = res.data;
						let transPixels = [];
						for (let i = 0; i < pixels.length; i += 4) {
							if (pixels[i + 3] < 128) {
								transPixels.push(pixels[i + 3]);
							}
						}
						var percent = (transPixels.length / (pixels.length / 4) * 100).toFixed(2);
						if (percent >= this.percentage) {
							this.scrapingSuccess();
						}
					},
					fail: (e) => {
						console.log(e);
					},
				}, this);
			},
			// 成功，清除所有图层
			scrapingSuccess(e) {
				if (this.endState) {
					return;
				}
				this.endState = true;
				this.ctx.moveTo(0, 0); // 把路径移动到画布中的指定点，不创建线条。用 stroke() 方法来画线条。
				this.ctx.clearRect(0, 0, this.width, this.height); // 清除画布上在该矩形区域内的内容(x,y,宽，高)。
				this.ctx.stroke(); // 画出当前路径的边框。默认颜色色为黑色。
				this.ctx.draw(true);
				// 弹出奖品
				setTimeout(()=>{
					this.result_show = true;
					this.drawInit();
					this.wtf = true;
					this.prizeTitle = "";
					this.prizeUrl = "";
				},800)
			},
			init(){
				if(this.userInfo){
					this.getInfo()
				}else{
					setTimeout(()=>{
						this.init()
					},500)
				}
			},
			getInfo(){
				luckDrawInfo.getDetail({id:this.id}).then(res => {
					this.luckDrawInfo=res.data
					this.total=res.data.my_can_num
					this.action('lottery',this.id,0,2,this.luckDrawInfo.title,'','lottery')
				})
			},
			choiseAddress(){
				this.currentPrize.is_address==1?uni.navigateTo({
						url:'/pages/address/address'
					}):''
				this.result_show=false
			},
			choiseAddress1(data){
				this.currentPrize=data
				uni.navigateTo({
					url:'/pages/address/address'
				})
				this.prize_show=false
			},
			setAddress(id){
				luckDrawInfo.setAddress({address_id:id,history_id:this.currentPrize.history_id||this.currentPrize.id}).then(res => {
					uni.showToast({
						title:"地址设置成功",
						icon:'none'
					})
				})
			},
			getRule(){
				this.scrapingSuccess();
				setTimeout(()=>{
					this.rule_show = true;
				},800)
			},
			getResult(){
				// if(!this.wtf){
				// 	return false
				// }
				this.scrapingSuccess();
				luckDrawInfo.getResult({lottery_id:this.id}).then(res => {
					this.list=res.data.data
					this.prize_show=true
				})
			},
			// 点击开始,请求接口抽奖
			startPlay(index) {
				if(this.luckDrawInfo.is_register==1&&!this.userInfo.type){
					uni.navigateTo({
						url:'/pages/login/login'
					})
					return false
				}
				if(this.luckDrawInfo.is_form==1&&this.luckDrawInfo.user_form_count==0){
					uni.navigateTo({
						url:'/pages/form/form?id='+this.luckDrawInfo.form_id+'&type_id=' + this.id + '&type=lottery'
					})
					return false
				}
				if(!this.wtf){
					return false
				}
				
				// 活动未开始或活动已结束
				let startTimeMs = new Date(this.luckDrawInfo.start_time).getTime();
				let endTimeMs = new Date(this.luckDrawInfo.end_time).getTime();
				let nowTimeMs = new Date().getTime();
				if (nowTimeMs < startTimeMs) {
					uni.showToast({
						icon: "none",
						title: "活动未开始"
					})
					return false;
				}
				if (nowTimeMs > endTimeMs) {
					uni.showToast({
						icon: "none",
						title: "活动已结束"
					})
					return false;
				}
				
				this.mask = false;
				this.wtf = false;
				luckDrawInfo.run({id:this.id}).then(res => {
					this.currentPrize = res.data;
					this.total = res.data.row_lottery_new.my_can_num;
					this.prizeTitle = res.data.title;
					this.prizeUrl = res.data.img;
				}).catch(err => {
					this.wtf = true;
				});
			}
		}
	}
</script>

<style scoped lang="scss">
	@import 'index.scss';
	/**/
</style>

scss代码：


.page{
	width: 750rpx;
	height: 100vh;
	position: relative;
}

.bg{
	width: 750rpx;
	height: 100vh;
}

.content{
	width: 750rpx;
	min-height: 100vh;
	height: 1448rpx;
	position: absolute;
	top: 0;
	left: 0;
}


.logo{
	height: 60rpx;
	display: flex;
	justify-content: center;
	margin-top: 90rpx;
	
	image{
		height: 60rpx;
	}
}

.title{
	height: 254rpx;
	display: flex;
	justify-content: center;
	margin-top: 20rpx;
	
	image{
		width: 640rpx;
		height: 254rpx;
	}
}

.notification{
	width: 370rpx;
	height: 56rpx;
	display: flex;
	justify-content: space-between;
	align-items: center;
	margin: -60rpx auto 0 auto;
		
	view{
		width: 26rpx;
		height: 4rpx;
		background-color: #fff;
	}
	text{
		font-size: 38rpx;
		font-family: PingFangSC-Medium, PingFang SC;
		font-weight: 500;
		color: #FFFFFF;
	}
}


.box{
	width: 658rpx;
	height: 422rpx;
	margin: 110rpx auto 0 auto;
	position: relative;
	
	.scrapingBg{
		width: 100%;
		height: 100%;
	}
		
	.scrapingBox{
		width: 100%;
		height: 100%;
		position: absolute;
		left: 0;
		top: 0;
		box-sizing: border-box;
		padding: 52rpx 62rpx;
		
		.scrapingBoxContent{
			width: 536rpx;
			height: 318rpx;
			z-index: 2;
			position: relative;
			
			image{
				width: 100%;
				height: 100%;
			}
			view {
				width: 100%;
				height: 100%;
				display: flex;
				justify-content: center;
				align-items: center;
				font-size: 100rpx;
				color: #1B9AF9;
				text-shadow: 0px 4px 8px rgba(149,216,255,0.5);
			}
		}
	}
}

.count{
	display: flex;
	justify-content: center;
	margin-top: 44rpx;
	
	.tip{
		font-size: 28rpx;
		font-family: PingFangSC-Medium, PingFang SC;
		font-weight: 500;
		color: #777777;
		text{
			color: #0039AF;
		}
	} 
}

.btns{
	display: flex;
	align-items: center;
	justify-content: space-between;
	margin-top: 26rpx;
}
	
.btn{
	width: 376rpx;
	height: 166rpx;
	position: relative;
	.btnImg{
		width: 100%;
		height: 100%;
	}
		
	.btnConent{
		width: 100%;
		position: absolute;
		top: 50%;
		transform: translateY(-100%);
		display: flex;
		justify-content: center;
		align-items: center;
		image{
			width: 42rpx;
			height: 42rpx;
			margin-right: 12rpx;
		}
		text{
			font-size: 42rpx;
			font-family: PingFangSC-Medium, PingFang SC;
			font-weight: 500;
			color: #FFFFFF;
		}
	}
	
}
	

.win{
	width: 750rpx;
	height: 100vh;
	background: rgba(0, 0, 0, 0.8);
	position: fixed;
	top: 0;
	left: 0;
	z-index: 2;
	display: flex;
	flex-direction: column;
	align-items: center;
	justify-content: center;
}

.win_box{
	width: 662rpx;
	height: 60%;
	padding: 40rpx;
	box-sizing: border-box;
	border-radius: 24rpx;
}

.win_box_bg{
	background: #C3E5FE;
}

.bg3{
	background: #C3E5FE;
}

.iconcolseIcon{
	font-size: 58rpx;
	margin-top: 98rpx;
}

.win_box1{
	width: 630rpx;
	height: 922rpx;
	position: relative;
}

.win_bg{
	width: 630rpx;
	height: 922rpx;
}

.win_content{
	width: 630rpx;
	height: 922rpx;
	position: absolute;
	left: 0;
	top: 0;
	display: flex;
	flex-direction: column;
	align-items: center;
}

.win_tips{
	font-size: 48rpx;
	font-family: SourceHanSansSC-Medium, SourceHanSansSC;
	font-weight: bold;
	margin-top: 290rpx;
}

.win_title{
	font-size: 48rpx;
	font-family: SourceHanSansSC-Medium, SourceHanSansSC;
	font-weight: bold;
	color: #FE6631;
	margin: 170rpx 0;
}

.win_btn{
	width: 280rpx;
	height: 80rpx;
	line-height: 80rpx;
	text-align: center;
	background: #FFE047;
	border-radius: 46rpx;
	font-size: 32rpx;
	font-family: SourceHanSansSC-Medium, SourceHanSansSC;
	font-weight: bold;
	color: #13112C;
}

.win_tit{
	font-size: 48rpx;
	font-family: SourceHanSansSC-Medium, SourceHanSansSC;
	font-weight: bold;
	margin-bottom: 32rpx;
}

.win_box2{
	width: 662rpx;
	height: 900rpx;
	background: #FFFFFF;
	border-radius: 24rpx;
	display: flex;
	flex-direction: column;
}

.items{
	width: 662rpx;
	height: 108rpx;
	background: #C3E5FE;
	border-radius: 24rpx 24rpx 0rpx 0rpx;
	display: flex;
	align-items: center;
	flex-shrink:0
}

.left,.right{
	width: 50%;
	text-align: center;
	font-family: SourceHanSansSC-Medium, SourceHanSansSC;
	font-weight: bold;
}

.i_title{
	font-size: 36rpx;
}

.list{
	height: 792rpx;
	padding-bottom: 20rpx;
	overflow: hidden;
}

.item{
	width: 662rpx;
	height: 88rpx;
	display: flex;
	align-items: center;
	justify-content: space-around;
}

.item:nth-child(2n){
	background-color: #F4F4F4;
}

.r_btn{
	width: 160rpx;
	height: 60rpx;
	line-height: 60rpx;
	text-align: center;
	background: #FFC659;
	border-radius: 46rpx;
	font-family: SourceHanSansSC-Medium, SourceHanSansSC;
	font-weight: bold;
	font-size: 32rpx;
	margin:0 auto;
}

效果: