HarmonyOS pixelMap

请参考下面demo：

pixelMap2base64(pixelMap: image.PixelMap){
  const imagePackerApi: image.ImagePacker = image.createImagePacker();
  let packOpts: image.PackingOption = { format: "image/jpeg", quality: 98 };
  imagePackerApi.packing(pixelMap, packOpts)
    .then((data: ArrayBuffer) => {
      console.info('packing succeeded.');
      let bufferArr = new Uint8Array(data)
      let help = new util.Base64Helper
      this.pixel = help.encodeToStringSync(bufferArr)
      console.log("base64 =>    " + this.pixel)
    }).catch((error: BusinessError) => {
    console.error('packing failed.');
  })
}