element-ui upload组件上传图片时限制图片宽高

template部分代码，引入upload组件，这里采用自动上传文件

<div class="filesC">
       <el-upload
         ref="files"
         name="imgFile"
         class="avatar-uploader"
         :with-credentials="true"
         :action="action"
         :show-file-list="false"
         :on-success="handleAvatarSuccess"
         :on-error="handleAvatarError"
         :before-upload="beforeAvatarUpload">
         <img v-if="imageUrl" :src="imageUrl" class="avatar">
         <i v-else class="el-icon-plus avatar-uploader-icon"></i>
       </el-upload>
       &nbsp;图片尺寸：141*54
</div>

script部分代码，图片上传之前触发 beforeAvatarUpload ，在这里return false 会中断上传操作

beforeAvatarUpload (file) {
  let _this = this
  if (file.type.indexOf('image')<0) {
    this.$alert({message: '图片格式不正确', btn: false})
    return false
  }
  const isLt2M = file.size / 1024 / 1024 < 2;
  const isSize = new Promise(function(resolve, reject) {
    let width = 141;
    let height = 54;
    let _URL = window.URL || window.webkitURL;
    let img = new Image();
    img.onload = function() {
      let valid = img.width == width && img.height == height;
      valid ? resolve() : reject();
    }
    img.src = _URL.createObjectURL(file);
  }).then(() => {
    return file;
  }, () => {
    _this.$alert({message: '上传的icon必须是等于141*54!', btn: false})
    return Promise.reject();
  });
  return isSize
},
handleAvatarSuccess (res, file) {
  if (res.state==200) {
    this.imageUrl = URL.createObjectURL(file.raw);//从文件中读取的本地文件路径，用于显示在img标签里
    this.fileUrl = res.data//上传成功后，后台给返回的图片线上路径
  }else{
    this.$alert({message: '上传失败', btn: false})
  }

},
handleAvatarError (res, file) {
  this.$alert({message: '选择图片失败', btn: false})
  /*this.imageUrl = URL.createObjectURL(file.raw);*/
},

css代码，修改原组件的样式

.filesC .avatar-uploader .el-upload {
  border: 1px solid #aaa;
  border-radius: 6px;
  cursor: pointer;
  position: relative;
  overflow: hidden;
}
.filesC .avatar-uploader .el-upload:hover {
  border-color: #409EFF;
}
.filesC .avatar-uploader-icon {
  font-size: 20px;
  color: #8c939d;
   141px;
  height: 54px;
  line-height: 54px;
  text-align: center;
  background: white;
}
.filesC .avatar {
   141px;
  height: 54px;
  display: block;
}