HarmonyOS 应用往图库里，新建指定目录，在该目录中，新增或删除指定图片或视频

async saveImage(buffer: ArrayBuffer | string): Promise<void> { 
  let context = getContext(this) as common.UIAbilityContext; 
  let helper = photoAccessHelper.getPhotoAccessHelper(context); 
  let uri = await helper.createAsset(photoAccessHelper.PhotoType.IMAGE, 'jpg'); 
  let file = await fs.open(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE); 
  await fs.write(file.fd, buffer); 
  await fs.close(file.fd); 
}

async pickerSave(buffer: ArrayBuffer | string): Promise<void> { 
  const photoSaveOptions = new picker.PhotoSaveOptions(); // 创建文件管理器保存选项实例 
  photoSaveOptions.newFileNames = ['PhotoViewPicker ' + new Date().getTime() + 'jpg'] // 保存文件名（可选） 
  const photoViewPicker = new picker.PhotoViewPicker; 
  photoViewPicker.save(photoSaveOptions) 
  .then(async (photoSvaeResult) => { 
  console.info('PhotoViewPicker.save successfully,photoSvaeResult uri:' + JSON.stringify(photoSvaeResult)); 
  let uri = photoSvaeResult[0]; 
  let file = await fs.open(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE); 
  await fs.write(file.fd, buffer); 
  await fs.close(file.fd); 
  promptAction.showToast({ 
    message: $r('app.string.image_request_success'), 
    duration: 2000 
  }) 
}) 
}