HarmonyOS 如何获取图片是多少kb的

可以通过photoAccessHelper.getAssets接口获取对应uri的PhotoAsset对象。这种方式获取的对象读取PhotoKeys.SIZE可以获取文件大小，

具体可参考以下代码：

import picker from '@ohos.file.picker';
import { photoAccessHelper } from '@kit.MediaLibraryKit';
import dataSharePredicates from '@ohos.data.dataSharePredicates';

let uris: Array<string> = [];
const context = getContext(this);
@Entry
@Component
struct Index {
  async photoPick() {
    let PhotoSelectOptions = new picker.PhotoSelectOptions();
    PhotoSelectOptions.MIMEType = picker.PhotoViewMIMETypes.IMAGE_TYPE;
    PhotoSelectOptions.maxSelectNumber = 5;
    let photoPicker = new picker.PhotoViewPicker();
    photoPicker.select(PhotoSelectOptions)
      .then(async (PhotoSelectResult: picker.PhotoSelectResult) => {
        console.info('PhotoViewPicker.select successfully, PhotoSelectResult uri: ' + JSON.stringify(PhotoSelectResult));
        uris = PhotoSelectResult.photoUris;
        //调用getAssets接口获取ri对应的PhotoAsset对象，然后通过获取的对象使用PhotoKeys.SIZE获取文件大小
        this.uriGetAssets()
      });
  }
  async uriGetAssets() {
  try {
    let phAccessHelper = photoAccessHelper.getPhotoAccessHelper(context);
    let predicates: dataSharePredicates.DataSharePredicates = new dataSharePredicates.DataSharePredicates();
    // 配置查询条件，使用PhotoViewPicker选择图片返回的uri进行查询
    predicates.equalTo('uri', uris[0]);
    let fetchOption: photoAccessHelper.FetchOptions = {
      fetchColumns: [],
      predicates: predicates
    };
    let fetchResult: photoAccessHelper.FetchResult<photoAccessHelper.PhotoAsset> = await phAccessHelper.getAssets(fetchOption);
    // 得到uri对应的PhotoAsset对象，读取文件的部分信息
    const asset: photoAccessHelper.PhotoAsset = await fetchResult.getFirstObject();
    console.info('asset size: ', asset.get(photoAccessHelper.PhotoKeys.SIZE));
  } catch (error){
    console.error('uriGetAssets failed with err: ' + JSON.stringify(error));
  }
}
  build() {
    Column(){
      Button("选取图片并获取图片大小").onClick(async () => this.photoPick())
    }
  }
}