def __init__(self, fp, stop_when=None, force=False):
"""Read the preamble and meta info and prepare iterator for remainder of file.
Parameters
----------
fp : an open DicomFileLike object, at start of file
force : boolean
Force reading of data. See ``read_file`` for more parameter info.
Adds flags to fp: Big/Little-endian and Implicit/Explicit VR
"""
self.fp = fp
self.stop_when = stop_when
self.preamble = preamble = read_preamble(fp, force)
self.has_header = has_header = (preamble is not None)
self.file_meta_info = Dataset()
if has_header:
self.file_meta_info = file_meta_info = _read_file_meta_info(fp)
transfer_syntax = file_meta_info.TransferSyntaxUID
if transfer_syntax == pydicom.uid.ExplicitVRLittleEndian:
self._is_implicit_VR = False
self._is_little_endian = True
elif transfer_syntax == pydicom.uid.ImplicitVRLittleEndian:
self._is_implicit_VR = True
self._is_little_endian = True
elif transfer_syntax == pydicom.uid.ExplicitVRBigEndian:
self._is_implicit_VR = False
self._is_little_endian = False
elif transfer_syntax == pydicom.uid.DeflatedExplicitVRLittleEndian:
# See PS3.6-2008 A.5 (p 71) -- when written, the entire dataset
# following the file metadata was prepared the normal way,
# then "deflate" compression applied.
# All that is needed here is to decompress and then
# use as normal in a file-like object
zipped = fp.read()
# -MAX_WBITS part is from comp.lang.python answer:
# groups.google.com/group/comp.lang.python/msg/e95b3b38a71e6799
unzipped = zlib.decompress(zipped, -zlib.MAX_WBITS)
fp = BytesIO(unzipped) # a file-like object
self.fp = fp # point to new object
self._is_implicit_VR = False
self._is_little_endian = True
else:
# Any other syntax should be Explicit VR Little Endian,
# e.g. all Encapsulated (JPEG etc) are ExplVR-LE
# by Standard PS 3.5-2008 A.4 (p63)
self._is_implicit_VR = False
self._is_little_endian = True
else: # no header -- make assumptions
fp.TransferSyntaxUID = pydicom.uid.ImplicitVRLittleEndian
self._is_little_endian = True
self._is_implicit_VR = True
impl_expl = ("Explicit", "Implicit")[self._is_implicit_VR]
big_little = ("Big", "Little")[self._is_little_endian]
logger.debug("Using {0:s} VR, {1:s} Endian transfer syntax".format(
impl_expl, big_little))
def __init__(self, fp, stop_when=None, force=False):
"""Read the preamble and meta info and prepare iterator for remainder of file.
Parameters
----------
fp : an open DicomFileLike object, at start of file
force : boolean
Force reading of data. See ``read_file`` for more parameter info.
Adds flags to fp: Big/Little-endian and Implicit/Explicit VR
"""
self.fp = fp
self.stop_when = stop_when
self.preamble = preamble = read_preamble(fp, force)
self.has_header = has_header = (preamble is not None)
self.file_meta_info = Dataset()
if has_header:
self.file_meta_info = file_meta_info = _read_file_meta_info(fp)
transfer_syntax = file_meta_info.TransferSyntaxUID
if transfer_syntax == pydicom.uid.ExplicitVRLittleEndian:
self._is_implicit_VR = False
self._is_little_endian = True
elif transfer_syntax == pydicom.uid.ImplicitVRLittleEndian:
self._is_implicit_VR = True
self._is_little_endian = True
elif transfer_syntax == pydicom.uid.ExplicitVRBigEndian:
self._is_implicit_VR = False
self._is_little_endian = False
elif transfer_syntax == pydicom.uid.DeflatedExplicitVRLittleEndian:
# See PS3.6-2008 A.5 (p 71) -- when written, the entire dataset
# following the file metadata was prepared the normal way,
# then "deflate" compression applied.
# All that is needed here is to decompress and then
# use as normal in a file-like object
zipped = fp.read()
# -MAX_WBITS part is from comp.lang.python answer:
# groups.google.com/group/comp.lang.python/msg/e95b3b38a71e6799
unzipped = zlib.decompress(zipped, -zlib.MAX_WBITS)
fp = BytesIO(unzipped) # a file-like object
self.fp = fp # point to new object
self._is_implicit_VR = False
self._is_little_endian = True
else:
# Any other syntax should be Explicit VR Little Endian,
# e.g. all Encapsulated (JPEG etc) are ExplVR-LE
# by Standard PS 3.5-2008 A.4 (p63)
self._is_implicit_VR = False
self._is_little_endian = True
else: # no header -- make assumptions
fp.TransferSyntaxUID = pydicom.uid.ImplicitVRLittleEndian
self._is_little_endian = True
self._is_implicit_VR = True
impl_expl = ("Explicit", "Implicit")[self._is_implicit_VR]
big_little = ("Big", "Little")[self._is_little_endian]
logger.debug("Using {0:s} VR, {1:s} Endian transfer syntax".format(
impl_expl, big_little))
