vue3 el-upload 自动上传前压缩图片的大小

<template>
  <div class="component-upload-image">
    <el-upload
      multiple
      :action="uploadImgUrl"
      list-type="picture-card"
      :on-success="handleUploadSuccess"
      :before-upload="handleBeforeUpload"
      :limit="limit"
      :on-error="handleUploadError"
      :on-exceed="handleExceed"
      ref="imageUpload"
      :before-remove="handleDelete"
      :show-file-list="true"
      :headers="headers"
      :file-list="fileList"
      :on-preview="handlePictureCardPreview"
      :class="{ hide: fileList.length >= limit }"
    >
      <el-icon class="avatar-uploader-icon"><plus /></el-icon>
    </el-upload>
    <!-- 上传提示 -->
    <div class="el-upload__tip" v-if="showTip">
      请上传
      <template v-if="fileSize">
        大小不超过 <b style="color: #f56c6c">200KB</b>
      </template>
      <template v-if="fileType">
        格式为 <b style="color: #f56c6c">{{ fileType.join("/") }}</b>
      </template>
      的文件
    </div>

    <el-dialog
      v-model="dialogVisible"
      title="预览"
      width="800px"
      append-to-body
    >
      <img
        :src="dialogImageUrl"
        style="display: block; max-width: 100%; margin: 0 auto"
      />
    </el-dialog>
  </div>
</template>

<script setup>
import { getToken } from "@/utils/auth";
import { compressAccurately } from 'image-conversion'

const props = defineProps({
  modelValue: [String, Object, Array],
  // 图片数量限制
  limit: {
    type: Number,
    default: 1,
  },
  // 大小限制(MB)
  fileSize: {
    type: Number,
    default: 2,
  },
  // 文件类型, 例如['png', 'jpg', 'jpeg']
  fileType: {
    type: Array,
    default: () => ["png", "jpg", "jpeg"],
  },
  // 是否显示提示
  isShowTip: {
    type: Boolean,
    default: true
  },
  //文件类型(oss_file_type):头像-avatar 大门照片-door 广告-banner 证件-identity 合同-contract
  customerId:{
    type:String,
    default:''
  },

});

const { proxy } = getCurrentInstance();
const emit = defineEmits();
const number = ref(0);
const uploadList = ref([]);
const dialogImageUrl = ref("");
const dialogVisible = ref(false);
const baseUrl = '';
const uploadImgUrl = ref(import.meta.env.VITE_APP_BASE_API + `/common/image/upload/faceImg?customerId=${props.customerId}`); // 上传的图片服务器地址
const headers = ref({ Authorization: "Bearer " + getToken() });
const fileList = ref([]);
const showTip = computed(
  () => props.isShowTip && (props.fileType || props.fileSize)
);

watch(() => props.modelValue, val => {
  if (val) {
    // 首先将值转为数组
    const list = Array.isArray(val) ? val : props.modelValue.split(",");
    // 然后将数组转为对象数组
    fileList.value = list.map(item => {
      if (typeof item === "string") {
        if (item.indexOf(baseUrl) === -1) {
          item = { name: baseUrl + item, url: baseUrl + item };
        } else {
          item = { name: item, url: item };
        }
      }
      return item;
    });
  } else {
    fileList.value = [];
    return [];
  }
},{ deep: true, immediate: true });

 // 转base64
 function base64ConvertFile(urlData) {
      var arr = urlData.split(',')
      var type = arr[0].match(/:(.*?);/)[1]
      var fileExt = type.split('/')[1]
      var bstr = atob(arr[1])
      var n = bstr.length
      var u8arr = new Uint8Array(n)
      while (n--) {
        u8arr[n] = bstr.charCodeAt(n);
      }
      return new File([u8arr], `${(Math.random() + '').replace('.', '')}.` + fileExt, {
        type: type
      });
    }
    // 压缩图片
    function compressFile(file){
      return new Promise((resolve, reject) => {
          let reader = new FileReader();
          reader.readAsDataURL(file);
          reader.onload = (e) => {
            // 图片base64化
            const base64Str = e.target.result; // 转化后的base64字符串
            const img = new Image();
            img.src = base64Str;
            img.onload = () => {
              // 获取 canvas 元素
              let canvas = document.getElementById("uploadFileCanvas");
              if (!canvas) {
                let pobj = document.getElementsByTagName("body")[0];
                let canvasTag = document.createElement("canvas");
                canvasTag.style.display = "none";
                canvasTag.id = "uploadFileCanvas";
                pobj.appendChild(canvasTag);
                canvas = document.getElementById("uploadFileCanvas");
              }
              // 绘制图像到 canvas 有指定宽度用this.width，没有就用图片的原宽高
              canvas.width = img.width;
              canvas.height = img.height;
              let ctx = canvas.getContext("2d");
              ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
            // 使用 toDataURL 方法压缩图像
            let dataUrl = canvas.toDataURL("image/jpeg", 0.8);
              resolve(base64ConvertFile(dataUrl))
            };
          };
      });
    }

    
// 上传前loading加载
function handleBeforeUpload(file) {
  let isImg = false;
  if (props.fileType.length) {
    let fileExtension = "";
    if (file.name.lastIndexOf(".") > -1) {
      fileExtension = file.name.slice(file.name.lastIndexOf(".") + 1);
    }
    isImg = props.fileType.some(type => {
      if (file.type.indexOf(type) > -1) return true;
      if (fileExtension && fileExtension.indexOf(type) > -1) return true;
      return false;
    });
  } else {
    isImg = file.type.indexOf("image") > -1;
  }
  if (!isImg) {
    proxy.$modal.msgError(
      `文件格式不正确, 请上传${props.fileType.join("/")}图片格式文件!`
    );
    return false;
  }
  if (props.fileSize) {
    const isLt = file.size / 1024 / 1024 < props.fileSize;
    if (!isLt) {
      proxy.$modal.msgError(`上传头像图片大小不能超过 ${props.fileSize} MB!`);
      return false;
    }
  }
    // 上传前压缩图片
    const compressedFile = compressFile(file);
    // 执行上传
    proxy.$modal.loading("正在上传图片，请稍候...");
    number.value++;
    return compressedFile;
}

// 文件个数超出
function handleExceed() {
  proxy.$modal.msgError(`上传文件数量不能超过 ${props.limit} 个!`);
}

// 上传成功回调
function handleUploadSuccess(res, file) {
  if (res.code === 200) {
    uploadList.value.push({ name: res.data, url: res.data });
    uploadedSuccessfully();
  } else {
    number.value--;
    proxy.$modal.closeLoading();
    proxy.$modal.msgError(res.msg);
    proxy.$refs.imageUpload.handleRemove(file);
    uploadedSuccessfully();
  }
}

// 删除图片
function handleDelete(file) {
  const findex = fileList.value.map(f => f.name).indexOf(file.name);
  if (findex > -1 && uploadList.value.length === number.value) {
    fileList.value.splice(findex, 1);
    emit("update:modelValue", listToString(fileList.value));
    return false;
  }
}

// 上传结束处理
function uploadedSuccessfully() {
  if (number.value > 0 && uploadList.value.length === number.value) {
    fileList.value = fileList.value.filter(f => f.url !== undefined).concat(uploadList.value);
    uploadList.value = [];
    number.value = 0;
    emit("update:modelValue", listToString(fileList.value));
    proxy.$modal.closeLoading();
  }
}

// 上传失败
function handleUploadError() {
  proxy.$modal.msgError("上传图片失败");
  proxy.$modal.closeLoading();
}

// 预览
function handlePictureCardPreview(file) {
  console.log(file,'file')
  dialogImageUrl.value = file.url;
  dialogVisible.value = true;
}

// 对象转成指定字符串分隔
function listToString(list, separator) {
  let strs = "";
  separator = separator || ",";
  for (let i in list) {
    if (undefined !== list[i].url && list[i].url.indexOf("blob:") !== 0) {
      strs += list[i].url.replace(baseUrl, "") + separator;
    }
  }
  return strs != "" ? strs.substr(0, strs.length - 1) : "";
}
</script>

<style scoped lang="scss">
// .el-upload--picture-card 控制加号部分
:deep(.hide .el-upload--picture-card) {
    display: none;
}
</style>