Vue Canvas 实现电子签名 手写板

最近再做移动端电子签名，Vue+Canvas实现，移动端、PC端均可，也可以从github下载 。
我在做这个功能的时候参考了 这个代码，但是在移动端光标与实际划线有偏移，我在我的代码中修正了这个问题。

代码

<template>
      <section class="signature">
          <div class="signatureBox">
              <div class="canvasBox" ref="canvasHW">
                  <canvas ref="canvasF" @touchstart='touchStart' @touchmove='touchMove' @touchend='touchEnd' @mousedown="mouseDown" @mousemove="mouseMove" @mouseup="mouseUp"></canvas>
                  <div class="btnBox">
                      <div @click="overwrite">重写</div>
                      <div @click="commit">提交签名</div>
                  </div>   
              </div>
          </div>
          <img class="imgCanvas" :src="imgUrl">
      </section>    
</template>```

JS

<script>
  export default {
    data() {
      return {
        stageInfo:'',
        imgUrl:'',
        client: {},
        points: [],
        canvasTxt: null,
        startX: 0,
        startY: 0,
        moveY: 0,
        moveX: 0,
        endY: 0,
        endX: 0,
        w: null,
        h: null,
        isDown: false,
        isViewAutograph: this.$route.query.isViews > 0,
        contractSuccess: this.$route.query.contractSuccess
      }
    },
    mounted() {
      let canvas = this.$refs.canvasF
      canvas.height = this.$refs.canvasHW.offsetHeight - 500
      canvas.width = this.$refs.canvasHW.offsetWidth - 50
      this.canvasTxt = canvas.getContext('2d')
      this.stageInfo = canvas.getBoundingClientRect()
    },
    methods: {
      //mobile
      touchStart(ev) {
        ev = ev || event
        ev.preventDefault()
        if (ev.touches.length == 1) {
          let obj = {
            x: ev.targetTouches[0].clienX,
            y: ev.targetTouches[0].clientY,
          }
          this.startX = obj.x
          this.startY = obj.y
          this.canvasTxt.beginPath()
          this.canvasTxt.moveTo(this.startX, this.startY)
          this.canvasTxt.lineTo(obj.x, obj.y)
          this.canvasTxt.stroke()
          this.canvasTxt.closePath()
          this.points.push(obj)
        }
      },
      touchMove(ev) {
        ev = ev || event
        ev.preventDefault()
        if (ev.touches.length == 1) {
          let obj = {
            x: ev.targetTouches[0].clientX - this.stageInfo.left,
            y: ev.targetTouches[0].clientY - this.stageInfo.top
          }
          this.moveY = obj.y
          this.moveX = obj.x
          this.canvasTxt.beginPath()
          this.canvasTxt.moveTo(this.startX, this.startY)
          this.canvasTxt.lineTo(obj.x, obj.y)
          this.canvasTxt.stroke()
          this.canvasTxt.closePath()
          this.startY = obj.y
          this.startX = obj.x
          this.points.push(obj)
        }
      },
      touchEnd(ev) {
        ev = ev || event
        ev.preventDefault()
        if (ev.touches.length == 1) {
          let obj = {
            x: ev.targetTouches[0].clientX - this.stageInfo.left,
            y: ev.targetTouches[0].clientY - this.stageInfo.top
          }
          this.canvasTxt.beginPath()
          this.canvasTxt.moveTo(this.startX, this.startY)
          this.canvasTxt.lineTo(obj.x, obj.y)
          this.canvasTxt.stroke()
          this.canvasTxt.closePath()
          this.points.push(obj)
        }
      },
      //pc
      mouseDown(ev) {
        ev = ev || event
        ev.preventDefault()
        if (1) {
          let obj = {
            x: ev.offsetX,
            y: ev.offsetY
          }
          this.startX = obj.x
          this.startY = obj.y
          this.canvasTxt.beginPath()
          this.canvasTxt.moveTo(this.startX, this.startY)
          this.canvasTxt.lineTo(obj.x, obj.y)
          this.canvasTxt.stroke()
          this.canvasTxt.closePath()
          this.points.push(obj)
          this.isDown = true
        }
      },
      mouseMove(ev) {
        ev = ev || event
        ev.preventDefault()
        if (this.isDown) {
          let obj = {
            x: ev.offsetX,
            y: ev.offsetY
          }
          this.moveY = obj.y
          this.moveX = obj.x
          this.canvasTxt.beginPath()
          this.canvasTxt.moveTo(this.startX, this.startY)
          this.canvasTxt.lineTo(obj.x, obj.y)
          this.canvasTxt.stroke()
          this.canvasTxt.closePath()
          this.startY = obj.y
          this.startX = obj.x
          this.points.push(obj)
        }
      },
      mouseUp(ev) {
        ev = ev || event
        ev.preventDefault()
        if (1) {
          let obj = {
            x: ev.offsetX,
            y: ev.offsetY
          }
          this.canvasTxt.beginPath()
          this.canvasTxt.moveTo(this.startX, this.startY)
          this.canvasTxt.lineTo(obj.x, obj.y)
          this.canvasTxt.stroke()
          this.canvasTxt.closePath()
          this.points.push(obj)
          this.points.push({x: -1, y: -1})
          this.isDown = false
        }
      },
      //重写
      overwrite() {
        this.canvasTxt.clearRect(0, 0, this.$refs.canvasF.width, this.$refs.canvasF.height)
        this.points = []
      },
      //提交签名
      commit() {
        this.imgUrl=this.$refs.canvasF.toDataURL();
        console.log(this.$refs.canvasF.toDataURL()) //签名img回传后台
      }
    }
  }
</script>

CSS

<style scoped>
  .signatureBox {
    width: 100%;
    height: calc(100% - 50px);
    box-sizing: border-box;
    overflow: hidden;
    background: #fff;
    z-index: 100;
    display: flex;
    flex-direction: column;
  }
  .canvasBox {
    box-sizing: border-box;
    flex: 1;
  }
  canvas {
    border: 1px solid #7d7d7d;
  }
  .btnBox {
    padding: 10px;
    text-align: center;
  }
  .btnBox button:first-of-type {
    background: transparent;
    border-radius: 4px;
    height: 40px;
    width: 80px;
    font-size: 14px;
  }
  .btnBox button:last-of-type {
    background: #71b900;
    color: #fff;
    border-radius: 4px;
    height: 40px;
    width: 80px;
    font-size: 14px;
  }
</style>