Python DicomBytesIO.write方法代码示例

# 需要导入模块: from pydicom.filebase import DicomBytesIO [as 别名]
# 或者: from pydicom.filebase.DicomBytesIO import write [as 别名]
def write_data_element(fp, data_element, encodings=None):
    """Write the data_element to file fp according to
    dicom media storage rules.
    """
    # Write element's tag
    fp.write_tag(data_element.tag)

    # If explicit VR, write the VR
    VR = data_element.VR
    if not fp.is_implicit_VR:
        if len(VR) != 2:
            msg = ("Cannot write ambiguous VR of '{}' for data element with "
                   "tag {}.\nSet the correct VR before writing, or use an "
                   "implicit VR transfer syntax".format(
                       VR, repr(data_element.tag)))
            raise ValueError(msg)
        if not in_py2:
            fp.write(bytes(VR, default_encoding))
        else:
            fp.write(VR)
        if VR in extra_length_VRs:
            fp.write_US(0)  # reserved 2 bytes

    # write into a buffer to avoid seeking back which can be expansive
    buffer = DicomBytesIO()
    buffer.is_little_endian = fp.is_little_endian
    buffer.is_implicit_VR = fp.is_implicit_VR

    if data_element.is_raw:
        # raw data element values can be written as they are
        buffer.write(data_element.value)
        is_undefined_length = data_element.length == 0xFFFFFFFF
    else:
        if VR not in writers:
            raise NotImplementedError(
                "write_data_element: unknown Value Representation "
                "'{0}'".format(VR))

        encodings = encodings or [default_encoding]
        encodings = convert_encodings(encodings)
        writer_function, writer_param = writers[VR]
        is_undefined_length = data_element.is_undefined_length
        if VR in text_VRs or VR in ('PN', 'SQ'):
            writer_function(buffer, data_element, encodings=encodings)
        else:
            # Many numeric types use the same writer but with numeric format
            # parameter
            if writer_param is not None:
                writer_function(buffer, data_element, writer_param)
            else:
                writer_function(buffer, data_element)

    # valid pixel data with undefined length shall contain encapsulated
    # data, e.g. sequence items - raise ValueError otherwise (see #238)
    if is_undefined_length and data_element.tag == 0x7fe00010:
        val = data_element.value
        if (fp.is_little_endian and not
                val.startswith(b'\xfe\xff\x00\xe0') or
                not fp.is_little_endian and
                not val.startswith(b'\xff\xfe\xe0\x00')):
            raise ValueError('Pixel Data with undefined length must '
                             'start with an item tag')

    value_length = buffer.tell()
    if (not fp.is_implicit_VR and VR not in extra_length_VRs and
            not is_undefined_length):
        try:
            fp.write_US(value_length)  # Explicit VR length field is 2 bytes
        except struct.error:
            msg = ('The value for the data element {} exceeds the size '
                   'of 64 kByte and cannot be written in an explicit transfer '
                   'syntax. You can save it using Implicit Little Endian '
                   'transfer syntax, or you have to truncate the value to not '
                   'exceed the maximum size of 64 kByte.'
                   .format(data_element.tag))
            raise ValueError(msg)
    else:
        # write the proper length of the data_element in the length slot,
        # unless is SQ with undefined length.
        fp.write_UL(0xFFFFFFFF if is_undefined_length else value_length)

    fp.write(buffer.getvalue())
    if is_undefined_length:
        fp.write_tag(SequenceDelimiterTag)
        fp.write_UL(0)  # 4-byte 'length' of delimiter data item