Coverage for python / lsst / images / fits / __init__.py: 100%

1# This file is part of lsst-images. 

2# 

3# Developed for the LSST Data Management System. 

4# This product includes software developed by the LSST Project 

5# (https://www.lsst.org). 

6# See the COPYRIGHT file at the top-level directory of this distribution 

7# for details of code ownership. 

8# 

9# Use of this source code is governed by a 3-clause BSD-style 

10# license that can be found in the LICENSE file. 

11 

12"""Archive implementations for the FITS file format. 

13 

14The archives in this package define a FITS-based meta format with the 

15following layout: 

16 

17- A no-data primary HDU with the special header cards ``INDXADDR``, 

18 ``INDXSIZE``, ``JSONADDR``, and ``JSONSIZE``, which provide the offsets to 

19 and sizes of two special HDUs at the end of the file (see below). The 

20 primary header may also hold arbitrary cards exported by the top-level type 

21 being serialized or propagated as opaque metadata from a previous read. 

22 

23- Any number of "normal" image, compressed-image, and binary table HDUs. These 

24 have unique ``EXTNAME`` values that are the all-caps variants of a JSON 

25 Pointer (IETF RFC 6901) path in the special JSON HDU (see below), with no 

26 ``EXTVER`` or ``EXTLEVEL``. 

27 

28- A special binary table HDU holding JSON data. This binary table has a single 

29 variable-length array byte column (i.e. ``TFORM='PB'``) that holds UTF-8 JSON 

30 data. There is always at least one row, which holds the JSON representation 

31 of the top-level object being serialized. Additional rows may be present to 

32 hold additional JSON blocks that are logically nested within the main one, 

33 but have been moved outside it to keep the main block more compact (the main 

34 JSON block will have pointers back to these). 

35 

36- A special binary table HDU that acts as an index into all others, by holding 

37 byte offsets and sizes for all preceding HDUs along with their ``EXTNAME``, 

38 ``XTENSION``, and ``ZIMAGE`` header values. 

39 

40When images and tables are saved to a `FitsOutputArchive`, "normal" HDUs are 

41added to hold their binary data, and a small Pydantic model is returned 

42with a reference to that HDU for inclusion in the JSON tree. 

43""" 

44 

45from ._common import * 

46from ._input_archive import * 

47from ._output_archive import *