uniapp微信H5 dom转换成图片并下载（html2canvas ）

由于微信安全防控，我们无法直接生成并下载，但是可以打开图片后长按保存

1、npm依赖

 npm install html2canvas --save

2、引入

	import html2canvas from "html2canvas"

3、方法

exportCardAsImage() {
				const cardElement = this.$refs.card.$el;
				console.log(this.$refs.card);
				html2canvas(cardElement).then((canvas) => {
					const imageData = canvas.toDataURL('image/png');
					console.log("图片", imageData);
					this.pic(imageData)
				});
			},
			pic(src) {
				uni.previewImage({
					urls: Array.isArray(src) ? src : [src],
					current: '',
					success: function(res) {},
					fail: function(res) {},
					complete: function(res) {},
				});
			},

4、完整代码

<template>
	<view class="index">
		<view class="top">
			<view class="bg">
				<image src="../../static/electronic_card/bg.png"></image>
			</view>
		</view>
		<view class="main">
			<view class="card" ref="card">
				<image src="../../static/card/bg.png" mode=""></image>
				<view class="content">
					<view class="">
						<view class="logo">
							<image src="../../static/card/logo.png" mode=""></image>
						</view>
						<view class="txt">
							姓&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;名：张明磊
							<br>
							班&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;级：1901班
							<br>
							联系方式：18888888888
							<br>
							入学年份：2019
							<br>
							No：HURA258998
						</view>
					</view>
					<view class="img">
						<image src="../../static/card/head.png" mode=""></image>
					</view>
				</view>
			</view>
		</view>
		<view class="downbtn" @click="exportCardAsImage">查看与保存卡片</view>
	</view>
</template>

<script>
	import html2canvas from "html2canvas"

	import utlis from '../../common/utils.js'
	export default {
		mixins: [utlis],
		data() {
			return {

			}
		},
		onLoad() {

		},
		onUnload() {

		},
		methods: {
			exportCardAsImage() {
				const cardElement = this.$refs.card.$el;
				console.log(this.$refs.card);
				html2canvas(cardElement).then((canvas) => {
					const imageData = canvas.toDataURL('image/png');
					console.log("图片", imageData);
					this.pic(imageData)
				});
			},
			pic(src) {
				uni.previewImage({
					urls: Array.isArray(src) ? src : [src],
					current: '',
					success: function(res) {},
					fail: function(res) {},
					complete: function(res) {},
				});
			},

		}
	}
</script>

<style scoped lang="scss">
	page {
		background: #F9F9F9;
	}

	.index {
		width: 100vw;
		display: flex;
		flex-direction: column;
		// justify-content: center;
		align-items: center;
	}

	.top {
		width: 100vw;

		.bg {
			position: relative;
			z-index: 1;

			image {
				height: 554rpx;
				width: 100vw;
			}
		}
	}

	.main {
		position: relative;
		z-index: 2;
		margin-top: -100rpx;
		width: 716rpx;
		height: 402rpx;
		background: rgba(175, 0, 5, 0.78);
		border-radius: 16rpx 16rpx 16rpx 16rpx;
		opacity: 1;
		overflow: hidden;
		// background: url("../../static/card/bg.png") repeat fixed center;

		.card {
			position: relative;
			z-index: 1;
			padding: 30rpx;

			&>image {
				position: absolute;
				z-index: 1;
				top: 0;
				left: 0;
				width: 716rpx;
				height: 402rpx;
			}

			.content {
				position: relative;
				z-index: 2;
				display: flex;
				justify-content: space-between;

				.logo {
					image {
						width: 296rpx;
						height: 72rpx;
					}
				}

				.txt {
					line-height: 50rpx;
					font-size: 24rpx;
					color: #FFFFFF;
					font-weight: 400;
				}

				.img {
					display: flex;
					// justify-content: center;
					align-items: center;
					margin-right: 88rpx;

					image {
						width: 182rpx;
						height: 230rpx;
					}
				}
			}
		}


	}

	.downbtn {

		margin: 0;
		width: 690rpx;
		height: 104rpx;
		background: #AF0005;
		border-radius: 72rpx 72rpx 72rpx 72rpx;
		opacity: 1;
		color: #FFFFFF;
		font-weight: 500;
		line-height: 104rpx;
		text-align: center;
		margin-top: 76rpx;
	}
</style>