Gwcs

-------------------
New Features
^^^^^^^^^^^^

- ``gwcs.WCS`` now supports the ``world_axis_object_components`` and
``world_axis_object_classes`` methods of the low level WCS API as specified by
APE 14.

- Removed astropy-helpers from package. [249]

- Added a method ``fix_inputs`` which returns an unique WCS from a compound
WCS by fixing inputs. [254]

- Added two new transforms - ``ToDirectionCosines`` and ``FromDirectionCosines``. [256]

- Added new transforms ``WavelengthFromGratingEquation``, ``AnglesFromGratingEquation3D``. [259]

- ``gwcs.WCS`` now supports the new ``world_axis_names`` and
``pixel_axis_names`` properties on ``LowLevelWCS`` objects. [260]

- Update the ``StokesFrame`` to work for arrays of coordinates and integrate
with APE 14. [258]

- Added ``Snell3D``, ``SellmeierGlass`` and ``SellmeierZemax`` transforms. [270]

API Changes
^^^^^^^^^^^

- Changed the initialization of ``TemporalFrame`` to be consistent with other
coordinate frames. [242]

Bug Fixes
^^^^^^^^^

- Ensure that ``world_to_pixel_values`` and ``pixel_to_world_values`` always
accept and return floats, even if the underlying transform uses units. [248]

-------------------

New Features
^^^^^^^^^^^^

- Add a schema and tag for the Stokes frame. [164]

- Added ``WCS.pixel_shape`` property. [233]


Bug Fixes
^^^^^^^^^

- Update util.isnumerical(...) to recognize big-endian types as numeric. [225]

- Fixed issue in unified WCS API (APE14) for transforms that use
``Quantity``. [222]

- Fixed WCS API issues when ``output_frame`` is 1D, e.g. ``Spectral`` only. [232]

-------------------

New Features
^^^^^^^^^^^^

- Initializing a ``WCS`` object with a ``pipeline`` list now keeps
the complete ``CoordinateFrame`` objects in the ``WCS.pipeline``.
The effect is that a ``WCS`` object can now be initialized with
a ``pipeline`` from a different ``WCS`` object. [174]

- Implement support for astropy APE 14
(https://doi.org/10.5281/zenodo.1188875). [#146]

- Added a ``wcs_from_[points`` function which creates a WCS object
two matching sets of points ``(x,y)`` and ``(ra, dec)``. [42]

------------------

New Features
^^^^^^^^^^^^

- Added a ``TemporalFrame`` to represent relative or absolute time axes. [125]

- Removed deprecated ``grid_from_domain`` function and ``WCS.domain`` property. [119]

- Support for Python 2.x, 3.0, 3.1, 3.2, 3.3 and 3.4 was removed. [119]

- Add a ``coordinate_to_quantity`` method to ``CoordinateFrame`` which handles
converting rich coordinate input to numerical values. It is an inverse of the
``coordinates`` method. [133]

- Add a ``StokesFrame`` which converts from 'I', 'Q', 'U', 'V' to 0-3. [133]

- Support serializing the base ``CoordinateFrame`` class to asdf, by making
a specific tag and schema for ``Frame2D``. [150]

- Generalized the footrpint calculation to all output axes. [167]


API Changes
^^^^^^^^^^^

- The argument ``output="numerical_plus"`` was replaced by a bool
argument ``with_units``. [156]

- Added a new flag ``axis_type`` to the footprint method. It controls what
type of footprint to calculate. [167]

Bug Fixes
^^^^^^^^^

- Fixed a bug in ``bounding_box`` definition when the WCS has only one axis. [117]

- Fixed a bug in ``grid_from_bounding_box`` which caused the grid to be larger than
the image in cases when the bounding box is on the edges of an image. [121]

------------------

- ``LabelMapperRange`` now returns ``LabelMapperRange._no_label`` when the key is
not within any range. [71]

- ``LabelMapperDict`` now returns ``LabelMapperDict._no_label`` when the key does
not match. [72]

- Replace ``domain`` with ``bounding_box``. [74]

- Added a ``LabelMapper`` model where ``mapper`` is an instance of
`~astropy.modeling.Model`. [78]

- Evaluating a WCS with bounding box was moved to ``astropy.modeling``. [86]

- RegionsSelector now handles the case when a label does not have a corresponding
transform and returns RegionsSelector.undefined_transform_value. [86]

- GWCS now deals with axes types which are neither celestial nor spectral as "unknown"
and creates a transform equivalent to the FITS linear transform. [92]

----------------

New Features
^^^^^^^^^^^^
- Added ``wcs_from_fiducial`` function to wcstools. [34]
- Added ``domain`` to the WCS object. [36]
- Added ``grid_from_domain`` function. [36]
- The WCS object can return now an `~astropy.coordinates.SkyCoord`
or `~astropy.units.Quantity` object. This is triggered by a new
parameter to the ``__call__`` method, ``output`` which takes values
of "numericals" (default) or "numericals_plus". [64]

API_Changes
^^^^^^^^^^^
- Added ``atol`` argument to ``LabelMapperDict``, representing the absolute tolerance [29]
- The ``CoordinateFrame.transform_to`` method was removed [64]

Bug Fixes
^^^^^^^^^
- Fixed a bug in ``LabelMapperDict`` where a wrong index was used.[29]
- Changed the order of the inputs when ``LabelMapperArray`` is evaluated as
the inputs are supposed to be image coordinates. [29]
- Renamed variables in read_wcs_from_header to match loop variable [63]