【Vue】 签名组件

一、需求背景：

检查业务，检查完成后，执行人需要签字证明检查完成

二、实现效果：

三、技术实现

通过canvas转换成blob对象，可以上传到文件服务，或者是下载另存为到本地磁盘

注意重点，canvas的样式的宽高和dom对象宽高一定要一致才可以，否则无法在面板绘制线条！

<template>
  <el-dialog title="签名面板" :close-on-click-modal="false" append-to-body :visible.sync="visible" class="JNPF-dialog JNPF-dialog_center" lock-scroll width="600px">
    <canvas id="signatureCanvas" style="width: 500px; height: 300px;"></canvas>
    <span slot="footer" class="dialog-footer">
      <el-button @click="clearCanvas"> 清 除</el-button>
      <el-button @click="visible = false"> 取 消</el-button>
      <el-button type="primary" @click="dataFormSubmit()" :loading="btnLoading"> 确 定</el-button>
    </span>
  </el-dialog>
</template>

<script>
import request from '@/utils/request'

export default {
  name: 'SignPanel',
  components: {},
  props: {
    pathType: {
      type: String,
      require: true,
      default: 'annexpic'
    },
    apiData: {
      type: Object,
      require: true,
      default: () => {}
    }
  },
  data() {
    return {
      visible: false,
      btnLoading: false,
      canvasInstance: null,
      canvasContext: null,
      drawing: false,
      lastX: false,
      lastY: false
    }
  },
  mounted() {

  },
  methods: {
    init() {
      this.visible = true
      this.$nextTick(() => {
        this.initialCanvas()
      })
    },
    initialCanvas() {
      // 获取画布元素和上下文对象
      const canvas = document.getElementById('signatureCanvas')
      const ctx = canvas.getContext('2d');
      this.canvasInstance = canvas
      this.canvasContext = ctx

// 设置 canvas 的宽度和高度
      canvas.width = 500; // 根据需要设置
      canvas.height = 300; // 根据需要设置

      // // 初始化变量
      this.drawing = false
      this.lastX = 0
      this.lastY = 0
      const _that = this;


      // 处理鼠标按下事件
      canvas.addEventListener('mousedown', (e) => {
        _that.lastX = e.offsetX
        _that.lastY = e.offsetY
        _that.drawing=true;
      })

      // 处理鼠标移动事件
      canvas.addEventListener('mousemove', (e) => {
        if (!_that.drawing) return
        ctx.beginPath()
        ctx.moveTo(_that.lastX, _that.lastY)
        ctx.lineTo(e.offsetX , e.offsetY)
        ctx.stroke()
        ctx.closePath()
        _that.lastX = e.offsetX
        _that.lastY = e.offsetY
      })

      // 处理鼠标松开事件
      canvas.addEventListener('mouseup', (e) => {
        _that.drawing = false
      })

      // 处理鼠标离开事件
      canvas.addEventListener('mouseout', () => {
        _that.drawing = false
      })
    },
    dataFormSubmit() {
      this.toUploadSignPic()
    },
    dataURLtoBlob(dataUrl) {
      const arr = dataUrl.split(','), mime = arr[0].match(/:(.*?)/)[1]
      const bstr = atob(arr[1])
      let n = bstr.length
      const u8arr = new Uint8Array(n)
      while(n--){
        u8arr[n] = bstr.charCodeAt(n)
      }
      return new Blob([u8arr], {type:mime})
    },
    toUploadSignPic() {
      const dataUrl = this.canvasInstance.toDataURL('image/png')
      const blobData = this.dataURLtoBlob(dataUrl)
      // 创建 File 对象
      const fileName = 'image.png'
      const file = new File([blobData], fileName, {type: 'image/png'})
      const formData = new FormData()
      formData.append('file', file)
      this.uploadSignApi(formData).then(res => {
        if (res.code !== 200) return
        this.$emit('whenSuccess', res, file)
        this.visible = false
      }).catch(err => {
        this.$emit('whenError', err, file)
        this.visible = false
      })
    },
    toDownloadSignPic() {
      const dataUrl = this.canvasInstance.toDataURL('image/png')
      const link = document.createElement('a')
      link.href = dataUrl
      link.download = 'signature.png'
      link.click()
    },
    clearCanvas() {
      this.canvasContext.clearRect(0, 0,  this.canvasInstance.width,  this.canvasInstance.height)
    },
    uploadSignApi(formData) {
      const apiPath = `/api/file/Uploader/${this.pathType}`
      const param = this.apiData
      Object.keys(param).forEach(key => ( formData.append(key, param[key]) ))
      return request({
        url: apiPath,
        method: 'POST',
        headers: { 'Content-Type': 'multipart/form-data' },
        data: formData
      })
    }
  }
}
</script>

<style scoped lang="scss">
canvas {
  border: 1px solid #DCDFE6;
  cursor: crosshair;
  border-radius: 5px;
}
</style>

因为兼容现有系统的组件，我而外将框架自带的图片上传改造成签名上传组件

图片上传组件点击时一定会选取本地文件，为了解决这个问题我是选择直接隐藏了上传组件

改为追加了一个签名面板按钮，面板确认时，发射器回调到组件上传成功的回调

因为签名只存在一份，所以文件数量限制1即可，通过上传成功的回调就能拦截处理

<template>
  <div class="UploadFile-container">
    <el-button @click="openSignPanel" style="margin-right: 5px;">打开签名</el-button>
    <template v-if="fileList.length">
      <transition-group class="el-upload-list el-upload-list--picture-card" tag="ul" name="el-list">
        <li class="el-upload-list__item is-success" v-for="(file,index) in fileList"
            :key="file.fileId">
          <el-image :src="define.comUrl+file.url" class="el-upload-list__item-thumbnail" :preview-src-list="getImgList(fileList)" :z-index="10000" :ref="'image'+index">
          </el-image>
          <span class="el-upload-list__item-actions">
            <span class="el-upload-list__item-preview" @click="handlePictureCardPreview(index)">
              <i class="el-icon-zoom-in"></i>
            </span>
            <span v-if="!disabled" class="el-upload-list__item-delete" @click="handleRemove(index)">
              <i class="el-icon-delete"></i>
            </span>
          </span>
        </li>
      </transition-group>
    </template>
    <template v-if="!detailed">
      <el-upload
        v-show="false"
        :action="define.comUploadUrl+'/'+type"
        :headers="uploadHeaders" :data="params"
        ref="elUpload"
        :on-success="handleSuccess"
        :multiple="limit!==1"
        :show-file-list="false"
        accept="image/*"
        :before-upload="beforeUpload"
        :disabled="disabled"
        list-type="picture-card"
        :auto-upload="false"
        class="upload-btn">
        <i slot="default" class="el-icon-plus" disabled></i>
      </el-upload>
    </template>
    <template>
      <div class="el-upload__tip" slot="tip" v-if="tipText">{{ tipText }}</div>
    </template>

    <sign-panel
      :visible.sync="signPaneVisible"
      :path-type="type"
      :api-data="params"
      ref="signForm"
      @whenSuccess="signUploadSuccess"
      @whenError="signUploadError"
    />
  </div>
</template>

<script>
import emitter from 'element-ui/src/mixins/emitter'
import SignPanel from '@/components/Generator/components/Upload/SignPanel.vue'
import BigForm from '@/views/dp-mng/scr-se-check/big-form.vue'
let { methods: { dispatch } } = emitter
const units = {
  KB: 1024,
  MB: 1024 * 1024,
  GB: 1024 * 1024 * 1024
}
export default {
  name: 'UploadSign',
  components: { BigForm, SignPanel },
  props: {
    value: {
      type: Array,
      default: () => []
    },
    type: {
      type: String,
      default: 'annexpic'
    },
    disabled: {
      type: Boolean,
      default: false
    },
    detailed: {
      type: Boolean,
      default: false
    },
    showTip: {
      type: Boolean,
      default: false
    },
    limit: {
      type: Number,
      default: 0
    },
    accept: {
      type: String,
      default: 'image/*'
    },
    sizeUnit: {
      type: String,
      default: 'MB'
    },
    pathType: {
      type: String,
      default: 'defaultPath'
    },
    isAccount: {
      type: Number,
      default: 0
    },
    folder: {
      type: String,
      default: ''
    },
    fileSize: {
      default: 10
    },
    tipText: {
      type: String,
      default: ''
    }
  },
  data() {
    return {
      signPaneVisible: false,
      fileList: [],
      uploadHeaders: { Authorization: this.$store.getters.token },
    }
  },
  watch: {
    value: {
      immediate: true,
      handler(val) {
        this.fileList = Array.isArray(val) ? val : []
      }
    }
  },
  computed: {
    params() {
      return {
        pathType: this.pathType,
        isAccount: this.isAccount,
        folder: this.folder
      }
    }
  },
  methods: {
    signUploadSuccess(result, file) {
      this.handleSuccess(result, file, this.$refs.elUpload.fileList)
    },
    signUploadError() {
      console.log(result)
    },
    openSignPanel() {
      this.signPaneVisible = true
      this.$refs.signForm.init()
    },
    beforeUpload(file) {
      if (this.fileList.length >= this.limit) {
        this.handleExceed()
        return false
      }
      const unitNum = units[this.sizeUnit];
      if (!this.fileSize) return true
      let isRightSize = file.size / unitNum < this.fileSize
      if (!isRightSize) {
        this.$message.error(`图片大小超过${this.fileSize}${this.sizeUnit}`)
        return isRightSize;
      }
      let isAccept = new RegExp('image/*').test(file.type)
      if (!isAccept) {
        this.$message.error(`请上传图片`)
        return isAccept;
      }
      return isRightSize && isAccept;
    },
    handleSuccess(res, file, fileList) {
      if (this.fileList.length >= this.limit) return this.handleExceed()
      if (res.code == 200) {
        this.fileList.push({
          name: file.name,
          fileId: res.data.name,
          url: res.data.url
        })
        this.$emit('input', this.fileList)
        this.$emit('change', this.fileList)
        dispatch.call(this, 'ElFormItem', 'el.form.change', this.fileList)
      } else {
        this.$refs.elUpload.uploadFiles.splice(fileList.length - 1, 1)
        fileList.filter(o => o.uid != file.uid)
        this.$emit('input', this.fileList)
        this.$emit('change', this.fileList)
        dispatch.call(this, 'ElFormItem', 'el.form.change', this.fileList)
        this.$message({ message: res.msg, type: 'error', duration: 1500 })
      }
    },
    handleExceed(files, fileList) {
      this.$message.warning(`当前限制最多可以上传${this.limit}张图片`)
    },
    handlePictureCardPreview(index) {
      this.$refs['image' + index][0].clickHandler()
    },
    handleRemove(index) {
      this.fileList.splice(index, 1)
      this.$refs.elUpload.uploadFiles.splice(index, 1)
      this.$emit("input", this.fileList)
      this.$emit('change', this.fileList)
      dispatch.call(this, 'ElFormItem', 'el.form.change', this.fileList)
    },
    getImgList(list) {
      const newList = list.map(o => this.define.comUrl + o.url)
      return newList
    }
  }
}
</script>
<style lang="scss" scoped>
>>> .el-upload-list--picture-card .el-upload-list__item {
  width: 120px;
  height: 120px;
}
>>> .el-upload--picture-card {
  width: 120px;
  height: 120px;
  line-height: 120px;
}
.upload-btn {
  display: inline-block;
}
.el-upload__tip {
  color: #a5a5a5;
  word-break: break-all;
  line-height: 1.3;
  margin-top: 5px;
}
// .el-upload-list--picture-card {
//   display: inline-block;
//   height: 0;
// }
</style>

表单效果：