[DCMTK] decompress DICOM

    DJDecoderRegistration::registerCodecs(); // register JPEG codecs
    //DcmFileFormat fileformat;
    if (fileformat.loadFile(filePath.c_str()).good())
    {
        DcmDataset* dataset = fileformat.getDataset();

        // decompress data set if compressed
        if (dataset->chooseRepresentation(EXS_LittleEndianExplicit, NULL).good() &&
            dataset->canWriteXfer(EXS_LittleEndianExplicit))
        {
            fileformat.saveFile("test_decompressed.dcm", EXS_LittleEndianExplicit);
        }
    }
    DJDecoderRegistration::cleanup(); // deregister JPEG codecs