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- # -*- coding: utf-8 -*-
-
- import array
- from collections import namedtuple
- import struct
- from StringIO import StringIO
-
- field_of_view = namedtuple('FOV', ['number', 'x', 'y', 'z', 'pfs_offset'])
-
-
- class Nd2Parser(object):
- """
- Reads .nd2 files, provides an interface to the metadata, and generates numpy arrays from the image data.
-
- """
- CHUNK_HEADER = 0xabeceda
- CHUNK_MAP_START = "ND2 FILEMAP SIGNATURE NAME 0001!"
- CHUNK_MAP_END = "ND2 CHUNK MAP SIGNATURE 0000001!"
-
- def __init__(self, filename):
- self._absolute_start = None
- self._filename = filename
- self._fh = None
- self._chunk_map_start_location = None
- self._cursor_position = 0
- self._dimension_text = None
- self._label_map = {}
- self.metadata = {}
- self._read_map()
- self._parse_metadata()
-
- @property
- def _file_handle(self):
- if self._fh is None:
- self._fh = open(self._filename, "rb")
- return self._fh
-
- @property
- def _dimensions(self):
- if self._dimension_text is None:
- for line in self.metadata['ImageTextInfo']['SLxImageTextInfo'].values():
- if "Dimensions:" in line:
- metadata = line
- break
- else:
- raise ValueError("Could not parse metadata dimensions!")
- for line in metadata.split("\r\n"):
- if line.startswith("Dimensions:"):
- self._dimension_text = line
- break
- else:
- raise ValueError("Could not parse metadata dimensions!")
- return self._dimension_text
-
- @property
- def _image_count(self):
- return self.metadata['ImageAttributes']['SLxImageAttributes']['uiSequenceCount']
-
- @property
- def _sequence_count(self):
- return self.metadata['ImageEvents']['RLxExperimentRecord']['uiCount']
-
- def _parse_metadata(self):
- for label in self._label_map.keys():
- if label.endswith("LV!") or "LV|" in label:
- data = self._read_chunk(self._label_map[label])
- stop = label.index("LV")
- self.metadata[label[:stop]] = self._read_metadata(data, 1)
-
- def _read_map(self):
- """
- Every label ends with an exclamation point, however, we can't directly search for those to find all the labels
- as some of the bytes contain the value 33, which is the ASCII code for "!". So we iteratively find each label,
- grab the subsequent data (always 16 bytes long), advance to the next label and repeat.
-
- """
- self._file_handle.seek(-8, 2)
- chunk_map_start_location = struct.unpack("Q", self._file_handle.read(8))[0]
- self._file_handle.seek(chunk_map_start_location)
- raw_text = self._file_handle.read(-1)
- label_start = raw_text.index(Nd2Parser.CHUNK_MAP_START) + 32
-
- while True:
- data_start = raw_text.index("!", label_start) + 1
- key = raw_text[label_start: data_start]
- location, length = struct.unpack("QQ", raw_text[data_start: data_start + 16])
- if key == Nd2Parser.CHUNK_MAP_END:
- # We've reached the end of the chunk map
- break
- self._label_map[key] = location
- label_start = data_start + 16
-
- def _read_chunk(self, chunk_location):
- """
- Gets the data for a given chunk pointer
-
- """
- self._file_handle.seek(chunk_location)
- # The chunk metadata is always 16 bytes long
- chunk_metadata = self._file_handle.read(16)
- header, relative_offset, data_length = struct.unpack("IIQ", chunk_metadata)
- if header != Nd2Parser.CHUNK_HEADER:
- raise ValueError("The ND2 file seems to be corrupted.")
- # We start at the location of the chunk metadata, skip over the metadata, and then proceed to the
- # start of the actual data field, which is at some arbitrary place after the metadata.
- self._file_handle.seek(chunk_location + 16 + relative_offset)
- return self._file_handle.read(data_length)
-
- def _z_level_count(self):
- st = self._read_chunk(self._label_map["CustomData|Z!"])
- return len(array.array("d", st))
-
- def _parse_unsigned_char(self, data):
- return struct.unpack("B", data.read(1))[0]
-
- def _parse_unsigned_int(self, data):
- return struct.unpack("I", data.read(4))[0]
-
- def _parse_unsigned_long(self, data):
- return struct.unpack("Q", data.read(8))[0]
-
- def _parse_double(self, data):
- return struct.unpack("d", data.read(8))[0]
-
- def _parse_string(self, data):
- value = data.read(2)
- while not value.endswith("\x00\x00"):
- # the string ends at the first instance of \x00\x00
- value += data.read(2)
- return value.decode("utf16")[:-1].encode("utf8")
-
- def _parse_char_array(self, data):
- array_length = struct.unpack("Q", data.read(8))[0]
- return array.array("B", data.read(array_length))
-
- def _parse_metadata_item(self, data):
- new_count, length = struct.unpack("<IQ", data.read(12))
- length -= data.tell() - self._cursor_position
- next_data_length = data.read(length)
- value = self._read_metadata(next_data_length, new_count)
- # Skip some offsets
- data.read(new_count * 8)
- return value
-
- def _get_value(self, data, data_type):
- parser = {1: self._parse_unsigned_char,
- 2: self._parse_unsigned_int,
- 3: self._parse_unsigned_int,
- 5: self._parse_unsigned_long,
- 6: self._parse_double,
- 8: self._parse_string,
- 9: self._parse_char_array,
- 11: self._parse_metadata_item}
- return parser[data_type](data)
-
- def _read_metadata(self, data, count):
- data = StringIO(data)
- metadata = {}
- for _ in xrange(count):
- self._cursor_position = data.tell()
- header = data.read(2)
- if not header:
- break
- data_type, name_length = map(ord, header)
- name = data.read(name_length * 2).decode("utf16")[:-1].encode("utf8")
- value = self._get_value(data, data_type)
- if name not in metadata.keys():
- metadata[name] = value
- else:
- if not isinstance(metadata[name], list):
- # We have encountered this key exactly once before. Since we're seeing it again, we know we
- # need to convert it to a list before proceeding.
- metadata[name] = [metadata[name]]
- # We've encountered this key before so we're guaranteed to be dealing with a list. Thus we append
- # the value to the already-existing list.
- metadata[name].append(value)
- return metadata
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