Python 3: The VR 'OB' should not be prefixed with b'OB'.

[suever]

From samueljo...@gmail.com on April 12, 2014 13:52:26

In the method _write_file_meta_info, there is a "b" prefix for 'OB' in line 259, which is perhaps wrong and should just be a str:

if Tag((2, 1)) not in meta_dataset:
        meta_dataset.add_new((2, 1), b'OB', b"\0\1")   # file meta information version

This will later fail in write_data_element when

if in_py3:
            fp.write(bytes(VR, default_encoding))

... tries to convert VR to bytes but it has to be a string. Therefore my assumption is that b'OB' should not be prefixed. I am pretty sure you can decide if I am right or not without me making a minimal program that shows this error. But if you want me to, just give me a shout.

Version info: Python 3.4 on OS X on latest hg tip (changeset: 326:98b641dc8823)

Here is the code that I use to create the file_meta for the dicom file from scratch.

    file_meta = dicom.dataset.Dataset()
    file_meta.SourceApplicationEntityTitle = __file__
    file_meta.ImplementationVersionName = "0.1.2"
    # Secondary image storge
    file_meta.MediaStorageSOPClassUID = "1.2.840.10008.5.1.4.1.1.7"
    # Todo: Fixme: The next two would require to get an official ID that
    # can be used to derive an own UID for this software.
    file_meta.MediaStorageSOPInstanceUID = \
        "1.2.826.0.1.3680043.8.498.13215509892738242775390658"
    # # UID for this specific version of the software
    file_meta.ImplementationClassUID = \
        "1.2.826.0.1.3680043.8.498.132155098927382427736600651"

and here is where I create the DS and set some values...

     ds = dicom.dataset.Dataset()
     ds.preamble = b"\0"*128
     ds.file_meta = file_meta
     ds.is_little_endian = True
     ds.is_implicit_VR = True

and finally write the file

    dicom.dataset.FileDataset(outfile, ds, file_meta=file_meta,
                                  preamble=b"\0"*128).save_as(outfile)

I am sure, I could remove some stuff that is duplicate (for example the preamble), but I think this is somewhat unrelated.

Thanks for pydicom.

Original issue: http://code.google.com/p/pydicom/issues/detail?id=141

[suever]

From Suever@gmail.com on April 12, 2014 13:59:19

This issue was closed by revision 65a0131425db .

Status: Fixed

[suever]

From Suever@gmail.com on April 12, 2014 13:59:53

Thanks for the report. Should be functional now.