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# Licensed under a 3-clause BSD style license - see LICENSE.rst
from __future__ import print_function, division, absolute_import
# Note: This file incldues code dervived from pywcsgrid2
#
# This file contains Matplotlib transformation objects (e.g. from pixel to world
# coordinates, but also world-to-world).
import abc
import numpy as np
from matplotlib.path import Path
from matplotlib.transforms import Transform
from ... import units as u
from ...wcs import WCS
from ...wcs.utils import wcs_to_celestial_frame
from ...extern import six
from ...coordinates import (SkyCoord, frame_transform_graph,
SphericalRepresentation,
UnitSphericalRepresentation,
BaseCoordinateFrame)
@six.add_metaclass(abc.ABCMeta)
class CurvedTransform(Transform):
"""
Abstract base class for non-affine curved transforms
"""
input_dims = 2
output_dims = 2
is_separable = False
def transform_path(self, path):
"""
Transform a Matplotlib Path
Parameters
----------
path : :class:`~matplotlib.path.Path`
The path to transform
Returns
-------
path : :class:`~matplotlib.path.Path`
The resulting path
"""
return Path(self.transform(path.vertices), path.codes)
transform_path_non_affine = transform_path
@abc.abstractmethod
def transform(self, input):
raise NotImplementedError("")
@abc.abstractmethod
def inverted(self):
raise NotImplementedError("")
class WCSWorld2PixelTransform(CurvedTransform):
"""
WCS transformation from world to pixel coordinates
"""
def __init__(self, wcs, slice=None):
super(WCSWorld2PixelTransform, self).__init__()
self.wcs = wcs
if self.wcs.wcs.naxis > 2:
if slice is None:
raise ValueError("WCS has more than 2 dimensions, so ``slice`` should be set")
elif len(slice) != self.wcs.wcs.naxis:
raise ValueError("slice should have as many elements as WCS "
"has dimensions (should be {0})".format(self.wcs.wcs.naxis))
else:
self.slice = slice
self.x_index = slice.index('x')
self.y_index = slice.index('y')
else:
self.slice = None
@property
def input_dims(self):
return self.wcs.wcs.naxis
def transform(self, world):
"""
Transform world to pixel coordinates. You should pass in a NxM array
where N is the number of points to transform, and M is the number of
dimensions in the WCS. This then returns the (x, y) pixel coordinates
as a Nx2 array.
"""
if world.shape[1] != self.wcs.wcs.naxis:
raise ValueError("Second dimension of input values should match number of WCS coordinates")
if world.shape[0] == 0:
pixel = np.zeros((0, 2))
else:
pixel = self.wcs.wcs_world2pix(world, 1) - 1
if self.slice is None:
return pixel
else:
return pixel[:, (self.x_index, self.y_index)]
transform_non_affine = transform
def inverted(self):
"""
Return the inverse of the transform
"""
return WCSPixel2WorldTransform(self.wcs, slice=self.slice)
class WCSPixel2WorldTransform(CurvedTransform):
"""
WCS transformation from pixel to world coordinates
"""
def __init__(self, wcs, slice=None):
super(WCSPixel2WorldTransform, self).__init__()
self.wcs = wcs
self.slice = slice
if self.slice is not None:
self.x_index = slice.index('x')
self.y_index = slice.index('y')
@property
def output_dims(self):
return self.wcs.wcs.naxis
def get_coord_slices(self, xmin, xmax, ymin, ymax, nx, ny):
"""
Get a coordinate slice
"""
x = np.linspace(xmin, xmax, nx)
y = np.linspace(ymin, ymax, ny)
Y, X = np.meshgrid(y, x)
pixel = np.array([X.ravel(), Y.ravel()]).transpose()
world = self.transform(pixel)
return X, Y, [world[:, i].reshape(nx, ny).transpose() for i in range(self.wcs.wcs.naxis)]
def transform(self, pixel):
"""
Transform pixel to world coordinates. You should pass in a Nx2 array
of (x, y) pixel coordinates to transform to world coordinates. This
will then return an NxM array where M is the number of dimensions in
the WCS
"""
if self.slice is None:
pixel_full = pixel.copy()
else:
pixel_full = []
for index in self.slice:
if index == 'x':
pixel_full.append(pixel[:, 0])
elif index == 'y':
pixel_full.append(pixel[:, 1])
else:
pixel_full.append(index)
pixel_full = np.array(np.broadcast_arrays(*pixel_full)).transpose()
pixel_full += 1
if pixel_full.shape[0] == 0:
world = np.zeros((0, 2))
else:
world = self.wcs.wcs_pix2world(pixel_full, 1)
# At the moment, one has to manually check that the transformation
# round-trips, otherwise it should be considered invalid.
pixel_check = self.wcs.wcs_world2pix(world, 1)
with np.errstate(invalid='ignore'):
invalid = np.any(np.abs(pixel_check - pixel_full) > 1., axis=1)
world[invalid] = np.nan
return world
transform_non_affine = transform
def inverted(self):
"""
Return the inverse of the transform
"""
return WCSWorld2PixelTransform(self.wcs, slice=self.slice)
class CoordinateTransform(CurvedTransform):
def __init__(self, input_system, output_system):
super(CoordinateTransform, self).__init__()
self._input_system_name = input_system
self._output_system_name = output_system
if isinstance(self._input_system_name, WCS):
self.input_system = wcs_to_celestial_frame(self._input_system_name)
elif isinstance(self._input_system_name, six.string_types):
self.input_system = frame_transform_graph.lookup_name(self._input_system_name)
if self.input_system is None:
raise ValueError("Frame {0} not found".format(self._input_system_name))
elif isinstance(self._input_system_name, BaseCoordinateFrame):
self.input_system = self._input_system_name
else:
raise TypeError("input_system should be a WCS instance, string, or a coordinate frame instance")
if isinstance(self._output_system_name, WCS):
self.output_system = wcs_to_celestial_frame(self._output_system_name)
elif isinstance(self._output_system_name, six.string_types):
self.output_system = frame_transform_graph.lookup_name(self._output_system_name)
if self.output_system is None:
raise ValueError("Frame {0} not found".format(self._output_system_name))
elif isinstance(self._output_system_name, BaseCoordinateFrame):
self.output_system = self._output_system_name
else:
raise TypeError("output_system should be a WCS instance, string, or a coordinate frame instance")
if self.output_system == self.input_system:
self.same_frames = True
else:
self.same_frames = False
@property
def same_frames(self):
return self._same_frames
@same_frames.setter
def same_frames(self, same_frames):
self._same_frames = same_frames
def transform(self, input_coords):
"""
Transform one set of coordinates to another
"""
if self.same_frames:
return input_coords
x_in, y_in = input_coords[:, 0], input_coords[:, 1]
c_in = SkyCoord(x_in, y_in, unit=(u.deg, u.deg),
frame=self.input_system)
c_out = c_in.transform_to(self.output_system)
if issubclass(c_out.representation, (SphericalRepresentation, UnitSphericalRepresentation)):
lon = c_out.data.lon.deg
lat = c_out.data.lat.deg
else:
lon = c_out.spherical.lon.deg
lat = c_out.spherical.lat.deg
return np.concatenate((lon[:, np.newaxis], lat[:, np.newaxis]), axis=1)
transform_non_affine = transform
def inverted(self):
"""
Return the inverse of the transform
"""
return CoordinateTransform(self._output_system_name, self._input_system_name)
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