HarmonyOS 鸿蒙Next 拉起相册后选中的照片jpeg格式如何转换成nv21数据

楼主你的demo感觉有点问题，这边基于你的demo修改了下，可以参考注释内容

async convert() {
   // 拉起相册，选择图片
   try {
     // 1. 拉起相册，选择图片
     let PhotoSelectOptions = new photoAccessHelper.PhotoSelectOptions();
     PhotoSelectOptions.MIMEType = photoAccessHelper.PhotoViewMIMETypes.IMAGE_TYPE;
     PhotoSelectOptions.maxSelectNumber = 1; // 选择一张图片
     let photoPicker = new photoAccessHelper.PhotoViewPicker();
     let photoSelectResult: photoAccessHelper.PhotoSelectResult = await photoPicker.select(PhotoSelectOptions);

     if (!photoSelectResult || photoSelectResult.photoUris.length === 0) {
       console.error("No image selected");
       return;
     }

     let url = photoSelectResult.photoUris[0]; // 获取选中图片的URI

     // 2. 读取图片为buffer
     const file = fs.openSync(url, fs.OpenMode.READ_ONLY);
     const photoSize = fs.statSync(file.fd).size;
     let buffer = new ArrayBuffer(photoSize);
     fs.readSync(file.fd, buffer);
     fs.closeSync(file);

     // 3. 创建ImageSource并生成PixelMap
     const imageSource = image.createImageSource(buffer);
     const pixelMap = await imageSource.createPixelMap();

     // 4. 转换为NV21格式
     let targetPixelFormat = image.PixelMapFormat.NV21;
     await pixelMap.convertPixelFormat(targetPixelFormat);

     // 5. 读取转换后的像素数据
     const imageInfo = await pixelMap.getImageInfo();
     const readBuffer = new ArrayBuffer(imageInfo.size.width * imageInfo.size.height * 3 / 2); // NV21格式的大小
     await pixelMap.readPixelsToBuffer(readBuffer);

     // 6. 将NV21数据保存到沙箱
     const sandboxDir = getContext().filesDir; // 沙箱目录
     const filePath = `${sandboxDir}/image_nv21.bin`; // 保存路径
     let file1 = fs.openSync(filePath, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE);
     fs.writeSync(file1.fd, readBuffer);

     console.log("NV21 image saved to:", filePath);
   } catch (error) {
     console.error("Error occurred:", error);
   }
 }
 aboutToAppear(): void {
   this.convert()
 }
 

 沙箱文件