PixelMap类型怎么转换成Base64字符串

let resourceManager = getContext(this).resourceManager 
let imageArray = await resourceManager.getMediaContent($r('app.media.beer')); 
let pixelBuffer = new Uint8Array(imageArray).buffer as Object as ArrayBuffer 
let imageResource = image.createImageSource(pixelBuffer); 
let opts: image.DecodingOptions = { editable: true } 
let pixelMap = await imageResource.createPixelMap(opts); 
 
// 转换成base64 
const imagePackerApi: image.ImagePacker = image.createImagePacker(); 
let packOpts: image.PackingOption = { format: 'image/jpeg', quality: 100 }; 
imagePackerApi.packing(pixelMap, packOpts).then((data: ArrayBuffer) => { 
  let buf: buffer.Buffer = buffer.from(data); 
  this.base64 = 'data:image/jpeg;base64,' + buf.toString('base64', 0, buf.length); 
  console.info('base64: ' + this.base64); 
})