签名页的效果如图下所示：

封装的组件代码如下所示：

<template>
	<view>
		<view class="wrapper">
			<view class="handBtn">
				<button @click="handleReset" class="delBtn">清除</button>
				<button @click="handleSubmit" class="saveBtn">保存</button>
				<button @click="handleBack" class="subBtn">返回</button>
			</view>
			<view class="handCenter">
				<canvas class="handWriting" :disable-scroll="true" @touchstart="touchstart" @touchmove="touchmove"
					@touchend="touchend" canvas-id="myCanvas" :style="{width:width +'px',height:height +'px'}"></canvas>
				<!--用于旋转图片的canvas容器-->
				<canvas style="position: absolute" :style="{ width: height+'px', height: width+'px' }"
					canvas-id="myCanvas2"></canvas>
			</view>
			<view class="handRight">
				<view class="handTitle">请签名</view>
			</view>
		</view>
	</view>
</template>

<script>
	export default {
		data() {
			return {
				ctx: '', //绘图图像
				points: [], //路径点集合,
				width: 0, //绘图宽度
				height: 0, //绘图高度
				hasSign: false, //是否已签名
				isInit: false, //是否已触摸
			};
		},
		mounted() {
			const _self = this;
			this.ctx = uni.createCanvasContext('myCanvas', this); //创建绘图对象
			//设置画笔样式
			this.ctx.lineWidth = 4;
			this.ctx.lineCap = 'round';
			this.ctx.lineJoin = 'round';
			uni.getSystemInfo({
				success: function(res) {
					_self.width = res.windowWidth - 95;
					_self.height = res.windowHeight - 30;
				}
			});
		},
		methods: {
			/**
			 * 触摸开始，获取到起点			 
			 */
			touchstart: function(e) {
				if (!this.isInit) {
					this.isInit = true;
					this.handleReset();
				};
				let startX = e.changedTouches[0].x;
				let startY = e.changedTouches[0].y;
				let startPoint = {
					X: startX,
					Y: startY
				};
				this.points.push(startPoint);
				//每次触摸开始，开启新的路径
				this.ctx.beginPath();
			},
			/**
			 * 触摸移动，获取到路径点
			 */
			touchmove: function(e) {
				let moveX = e.changedTouches[0].x;
				let moveY = e.changedTouches[0].y;
				let movePoint = {
					X: moveX,
					Y: moveY
				};
				this.points.push(movePoint); //存点
				let len = this.points.length;
				if (len >= 2) {
					this.draw(); //绘制路径
				}
			},
			/**
			 *  触摸结束，将未绘制的点清空防止对后续路径产生干扰
			 */
			touchend: function() {
				this.points = [];
				this.ctx.draw(true);
			},
			/**
			 * 绘制笔迹
			 * 1.为保证笔迹实时显示，必须在移动的同时绘制笔迹
			 * 2.为保证笔迹连续，每次从路径集合中区两个点作为起点（moveTo）和终点(lineTo)
			 * 3.将上一次的终点作为下一次绘制的起点（即清除第一个点）
			 */
			draw: function() {
				let point1 = this.points[0];
				let point2 = this.points[1];
				this.points.shift();
				this.ctx.moveTo(point1.X, point1.Y);
				this.ctx.lineTo(point2.X, point2.Y);
				this.ctx.stroke();
				this.ctx.draw(true);
				this.hasSign = true;
			},
			//清空画布
			handleReset: function() {
				this.ctx.clearRect(0, 0, this.width, this.height);
				this.ctx.draw(true);
				this.hasSign = false;
			},
			/**
			 *保存签名
			 */
			handleSubmit() {
				const _self = this;
				if (!this.hasSign) {
					uni.showToast({
						title: '签名不能为空',
						icon: 'none',
						duration: 2000
					})
					return;
				}
				uni.canvasToTempFilePath({
					fileType: 'png',
					quality: 1, //图片质量
					canvasId: 'myCanvas',
					success(res) {
						uni.getImageInfo({
							// 获取图片的信息
							src: res.tempFilePath,
							success: (res1) => {
								// 将canvas1的内容复制到canvas2中
								let canvasContext = uni.createCanvasContext('myCanvas2', _self);
								canvasContext.translate(0, _self.width);
								canvasContext.rotate((-90 * Math.PI) / 180);
								canvasContext.drawImage(res.tempFilePath, 0, 0, _self.width, _self
									.height);
								canvasContext.draw(false, () => {
									// 将之前在绘图上下文中的描述（路径、变形、样式）画到 canvas 中
									uni.canvasToTempFilePath({
										// 把当前画布指定区域的内容导出生成指定大小的图片。在 draw() 回调里调用该方法才能保证图片导出成功。								
										fileType: 'png',
										quality: 1, //图片质量
										canvasId: 'myCanvas2',
										complete(res2) {
                                          //此处是将图片文件传给父级组件上传至后台
											_self.$emit("submitSignature", res2
												.tempFilePath);
										}
									}, _self)
								})
							}
						})
					}
				}, this)
			},
			//返回上级
			handleBack() {
				this.handleReset();
				this.$emit("close");
			},
		}
	};
</script>

<style>
	page {
		background: #fbfbfb;
		height: auto;
		overflow: hidden;
	}

	.wrapper {
		width: 100%;
		height: 95vh;
		margin: 15px 0;
		overflow: hidden;
		display: flex;
		align-content: center;
		flex-direction: row;
		justify-content: center;
		font-size: 28rpx;
	}

	.handWriting {
		background: #fff;
		width: 100%;
		height: 95vh;
	}

	.handRight {
		display: inline-flex;
		align-items: center;
		width: 45x;
	}

	.handCenter {
		border: 4rpx dashed #e9e9e9;
		flex: 1;
		overflow: hidden;
		box-sizing: border-box;
	}

	.handTitle {
		transform: rotate(90deg);
		flex: 1;
		color: #666;
		line-height: 100%;
	}

	.handBtn button {
		font-size: 28rpx;
	}

	.handBtn {
		height: 95vh;
		width: 50px;
		display: inline-flex;
		flex-direction: column;
		justify-content: space-between;
		align-content: space-between;
	}

	.delBtn {
		position: absolute;
		top: 250rpx;
		left: 0rpx;
		transform: rotate(90deg);
		color: #666;
	}

	.subBtn {
		position: absolute;
		bottom: 52rpx;
		left: -3rpx;
		display: inline-flex;
		transform: rotate(90deg);
		background: #008ef6;
		color: #fff;
		margin-bottom: 30rpx;
		text-align: center;
		justify-content: center;
	}

	.saveBtn {
		position: absolute;
		top: 375rpx;
		left: 0rpx;
		transform: rotate(90deg);
		color: #666;
	}
</style>

最后保存的图片是经过旋转后的。