如何将图片PixelMap压缩到指定大小

photoSelect() { 
  const photoSelectOptions = new picker.PhotoSelectOptions(); 
  photoSelectOptions.MIMEType = picker.PhotoViewMIMETypes.IMAGE_TYPE; 
  photoSelectOptions.maxSelectNumber = 5 
 
  const photoPicker = new picker.PhotoViewPicker(); 
  photoPicker.select(photoSelectOptions) 
    .then(async (photoSelectResult) => { 
      let uri = photoSelectResult.photoUris[0] 
      let file = fs.openSync(uri, fs.OpenMode.READ_ONLY) 
      this.compressPictures(file) 
 
    }) 
} 
 
compressPictures(file: fs.File, data?: ArrayBuffer, size: number = 30, quality: number = 99): void | ArrayBuffer { 
  if (data) { 
    const currentSize = data.byteLength / 1024 
    if (currentSize <= size || quality === 1) { 
      return data 
    } 
  } 
  const imagePackerApi = image.createImagePacker(); 
  const imageSourceApi = image.createImageSource(file.fd); 
  let packOpts: image.PackingOption = { format: “image/jpeg”, quality: quality } 
 
  imagePackerApi.packing(imageSourceApi, packOpts) 
    .then((ret: ArrayBuffer) => { 
      if (data && ret.byteLength === data.byteLength) { 
        return ret 
      } 
      return this.compressPictures(file, ret, size, quality-1) 
    }).catch((err: BusinessError) => { 
    console.log(lbh) 
    return false 
  }) 
}
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