HarmonyOS picker.pick API拍照的图片如何转换为base64编码

：

let packOpts: image.PackingOption = { format: "image/jpeg", quality: 98 };
let imagePackerApi = image.createImagePacker();
const context: Context = getContext(this);
const resourceMgr = context.resourceManager;
let imageBuffer = await resourceMgr.getMediaContent($r('app.media.ic_low'));
const imageSource: image.ImageSource = image.createImageSource(imageBuffer.buffer);
let decodingOptions: image.DecodingOptions = {
  editable: true,
  desiredPixelFormat: 3,
  rotate: 90
} // 创建pixelMap并进行简单的旋转和缩放 
imageSource.createPixelMap(decodingOptions).then((pixelMap: PixelMap) => {
  this.pixelMap = pixelMap
  // pixelmap 转base64 先要有一个packing的过程 
  imagePackerApi.packing(pixelMap, packOpts).then((data: ArrayBuffer) => {
    let base64Str = buffer.from(data).toString('base64')
    let resultBase64Str = "data:image/png;base64," + base64Str
    this.resultBase64Str = resultBase64Str
  }).catch((error: BusinessError) => {
    console.error('Failed to pack the image. And the error is: ' + error);
  })
  pixelMap.release();
})