WCS

class gwcs.wcs.WCS(forward_transform=None, input_frame=u'detector', output_frame=None, name=u'')

Bases: object

Basic WCS class.

Parameters:

forward_transform : Model or a list

The transform between input_frame and output_frame. A list of (frame, transform) tuples where frame is the starting frame and transform is the transform from this frame to the next one or output_frame. The last tuple is (transform, None), where None indicates the end of the pipeline.

input_frame : str, CoordinateFrame

A coordinates object or a string name.

output_frame : str, CoordinateFrame

A coordinates object or a string name.

name : str

a name for this WCS

Attributes Summary

available_frames	List all frames in this WCS object.
backward_transform	Return the total backward transform if available - from output to input coordinate system.
domain	Return the range of acceptable values for each input axis.
forward_transform	Return the total forward transform - from input to output coordinate frame.
input_frame	Return the input coordinate frame.
name	Return the name for this WCS.
output_frame	Return the output coordinate frame.
pipeline	Return the pipeline structure.
unit	The unit of the coordinates in the output coordinate system.

Methods Summary

__call__(*args, **kwargs)	Executes the forward transform.
footprint([domain, center])	Return the footprint of the observation in world coordinates.
get_transform(from_frame, to_frame)	Return a transform between two coordinate frames.
insert_transform(frame, transform[, after])	Insert a transform before (default) or after a coordinate frame.
invert(*args, **kwargs)	Invert coordnates.
set_transform(from_frame, to_frame, transform)	Set/replace the transform between two coordinate frames.
transform(from_frame, to_frame, *args, **kwargs)	Transform positions between two frames.

Attributes Documentation

available_frames

List all frames in this WCS object.

Returns:

available_frames : dict

{frame_name: frame_object or None}

backward_transform

Return the total backward transform if available - from output to input coordinate system.

Raises:

NotImplementedError :

An analytical inverse does not exist.

domain

Return the range of acceptable values for each input axis.

forward_transform

Return the total forward transform - from input to output coordinate frame.

input_frame

Return the input coordinate frame.

name

Return the name for this WCS.

output_frame

Return the output coordinate frame.

pipeline

Return the pipeline structure.

unit

The unit of the coordinates in the output coordinate system.

Methods Documentation

__call__(*args, **kwargs)

Executes the forward transform.

args : float or array-like

Inputs in the input coordinate system, separate inputs for each dimension.

output : str

One of [“numericals”, “numericals_plus”] If “numericals_plus” - returns a SkyCoord or Quantity object.

footprint(domain=None, center=True)

Return the footprint of the observation in world coordinates.

Parameters:

domain : slice or tuple of floats: (start, stop, step) or (start, stop) or (stop,)

size of image

center : bool

If True use the center of the pixel, otherwise use the corner.

Returns:

coord : (4, 2) array of (x, y) coordinates.

The order is counter-clockwise starting with the bottom left corner.

get_transform(from_frame, to_frame)

Return a transform between two coordinate frames.

Parameters:

from_frame : str or CoordinateFrame

Initial coordinate frame name of object.

to_frame : str, or instance of CoordinateFrame

End coordinate frame name or object.

Returns:

transform : Model

Transform between two frames.

insert_transform(frame, transform, after=False)

Insert a transform before (default) or after a coordinate frame.

Append (or prepend) a transform to the transform connected to frame.

Parameters:

frame : str or CoordinateFrame

Coordinate frame which sets the point of insertion.

transform : Model

New transform to be inserted in the pipeline

after : bool

If True, the new transform is inserted in the pipeline immediately after frame.

invert(*args, **kwargs)

Invert coordnates.

The analytical inverse of the forward transform is used, if available. If not an iterative method is used.

Parameters:

args : float, array like, SkyCoord or Unit

coordinates to be inverted

kwargs : dict

keyword arguments to be passed to the iterative invert method.

set_transform(from_frame, to_frame, transform)

Set/replace the transform between two coordinate frames.

Parameters:

from_frame : str or CoordinateFrame

Initial coordinate frame.

to_frame : str, or instance of CoordinateFrame

End coordinate frame.

transform : Model

Transform between from_frame and to_frame.

transform(from_frame, to_frame, *args, **kwargs)

Transform positions between two frames.

Parameters:

from_frame : str or CoordinateFrame

Initial coordinate frame.

to_frame : str, or instance of CoordinateFrame

Coordinate frame into which to transform.

args : float

input coordinates to transform

args : float or array-like

Inputs in from_frame, separate inputs for each dimension.

output : str

One of [“numericals”, “numericals_plus”] If “numericals_plus” - returns a SkyCoord or Quantity object.