WcsGeom¶
-
class
gammapy.maps.
WcsGeom
(wcs, npix, cdelt=None, crpix=None, axes=None, cutout_info=None)[source]¶ Bases:
gammapy.maps.Geom
Geometry class for WCS maps.
This class encapsulates both the WCS transformation object and the the image extent (number of pixels in each dimension). Provides methods for accessing the properties of the WCS object and performing transformations between pixel and world coordinates.
- Parameters
- wcs
WCS
WCS projection object
- npixtuple
Number of pixels in each spatial dimension
- cdelttuple
Pixel size in each image plane. If none then a constant pixel size will be used.
- crpixtuple
Reference pixel coordinate in each image plane.
- axeslist
Axes for non-spatial dimensions
- cutout_infodict
Dict with cutout info, if the
WcsGeom
was created byWcsGeom.cutout()
- wcs
Attributes Summary
If the geom contains an energy axis rename it to energy true
List of non-spatial axes.
Map coordinate of the center of the geometry.
Pixel coordinate of the center of the geometry.
Sky coordinate of the center of the geometry.
Cutout info dict.
Shape of the Numpy data array matching this geometry.
Coordinate system of the projection.
Flag for all-sky maps.
Whether the geom non spatial axes have length 1, i.e.
Whether the geom is an image without extra dimensions.
Is this geometry is regular in non-spatial dimensions (bool)?
Tuple with image dimension in pixels in longitude and latitude.
Pixel area in deg^2.
Pixel scale.
Map projection.
Shape of non-spatial axes.
WCS projection object.
Tuple with image dimension in deg in longitude and latitude.
Methods Summary
Bin volume (
Quantity
)contains
(coords)Check if a given map coordinate is contained in the geometry.
contains_pix
(pix)Check if a given pixel coordinate is contained in the geometry.
coord_to_idx
(coords[, clip])Convert map coordinates to pixel indices.
coord_to_pix
(coords)Convert map coordinates to pixel coordinates.
copy
(**kwargs)Copy and overwrite given attributes.
create
([npix, binsz, proj, frame, refpix, …])Create a WCS geometry object.
crop
(crop_width)Crop the geometry at the edges.
cutout
(position, width[, mode])Create a cutout around a given position.
downsample
(factor[, axis_name])Downsample the spatial dimension of the geometry by a given factor.
drop
(axis_name)Drop an axis from the geom.
energy_mask
([energy_min, energy_max, …])Create a mask for a given energy range.
from_hdulist
(hdulist[, hdu, hdu_bands])Load a geometry object from a FITS HDUList.
from_header
(header[, hdu_bands, format])Create a WCS geometry object from a FITS header.
get_coord
([idx, flat, mode, frame])Get map coordinates from the geometry.
get_idx
([idx, flat])Get tuple of pixel indices for this geometry.
get_image_shape
(idx)Get the shape of the image plane at index
idx
.get_pix
([idx, mode])Get map pix coordinates from the geometry.
is_aligned
(other[, tolerance])Check if WCS and extra axes are aligned.
pad
(pad_width)Pad the geometry at the edges.
pix_to_coord
(pix)Convert pixel coordinates to map coordinates.
pix_to_idx
(pix[, clip])Convert pixel coordinates to pixel indices.
region_mask
(regions[, inside])Create a mask from a given list of regions
resample_axis
(axis)Resample geom to a new axis binning.
separation
(center)Compute sky separation wrt a given center.
slice_by_idx
(slices)Create a new geometry by slicing the non-spatial axes.
Solid angle array (
Quantity
insr
).squash
(axis_name)Squash geom axis.
to_bands_hdu
([hdu, hdu_skymap, format])to_binsz
(binsz)Change pixel size of the geometry.
to_cube
(axes)Append non-spatial axes to create a higher-dimensional geometry.
to_image
()Create 2D image geometry (drop non-spatial dimensions).
upsample
(factor[, axis_name])Upsample the spatial dimension of the geometry by a given factor.
Attributes Documentation
-
as_energy_true
¶ If the geom contains an energy axis rename it to energy true
-
axes
¶ List of non-spatial axes.
-
center_coord
¶ Map coordinate of the center of the geometry.
- Returns
- coordtuple
-
center_pix
¶ Pixel coordinate of the center of the geometry.
- Returns
- pixtuple
-
cutout_info
¶ Cutout info dict.
-
data_shape
¶ Shape of the Numpy data array matching this geometry.
-
frame
¶ Coordinate system of the projection.
Galactic (“galactic”) or Equatorial (“icrs”).
-
is_allsky
¶ Flag for all-sky maps.
-
is_flat
¶ Whether the geom non spatial axes have length 1, i.e. if the geom is equivalent to an image.
-
is_hpx
= False¶
-
is_image
¶ Whether the geom is an image without extra dimensions.
-
is_regular
¶ Is this geometry is regular in non-spatial dimensions (bool)?
False for multi-resolution or irregular geometries.
True if all image planes have the same pixel geometry.
-
ndim
¶
-
npix
¶ Tuple with image dimension in pixels in longitude and latitude.
-
pixel_area
¶ Pixel area in deg^2.
-
pixel_scales
¶ Pixel scale.
Returns angles along each axis of the image at the CRPIX location once it is projected onto the plane of intermediate world coordinates.
- Returns
- angle:
Angle
- angle:
-
projection
¶ Map projection.
-
shape_axes
¶ Shape of non-spatial axes.
-
wcs
¶ WCS projection object.
-
width
¶ Tuple with image dimension in deg in longitude and latitude.
Methods Documentation
-
contains_pix
(pix)¶ Check if a given pixel coordinate is contained in the geometry.
- Parameters
- pixtuple
Tuple of pixel coordinates.
- Returns
- containment
ndarray
Bool array.
- containment
-
coord_to_idx
(coords, clip=False)¶ Convert map coordinates to pixel indices.
- Parameters
- coordstuple or
MapCoord
Coordinate values in each dimension of the map. This can either be a tuple of numpy arrays or a MapCoord object. If passed as a tuple then the ordering should be (longitude, latitude, c_0, …, c_N) where c_i is the coordinate vector for axis i.
- clipbool
Choose whether to clip indices to the valid range of the geometry. If false then indices for coordinates outside the geometry range will be set -1.
- coordstuple or
- Returns
- pixtuple
Tuple of pixel indices in image and band dimensions. Elements set to -1 correspond to coordinates outside the map.
-
coord_to_pix
(coords)[source]¶ Convert map coordinates to pixel coordinates.
- Parameters
- coordstuple
Coordinate values in each dimension of the map. This can either be a tuple of numpy arrays or a MapCoord object. If passed as a tuple then the ordering should be (longitude, latitude, c_0, …, c_N) where c_i is the coordinate vector for axis i.
- Returns
- pixtuple
Tuple of pixel coordinates in image and band dimensions.
-
copy
(**kwargs)¶ Copy and overwrite given attributes.
- Parameters
- **kwargsdict
Keyword arguments to overwrite in the map geometry constructor.
- Returns
- copy
Geom
Copied map geometry.
- copy
-
classmethod
create
(npix=None, binsz=0.5, proj='CAR', frame='icrs', refpix=None, axes=None, skydir=None, width=None)[source]¶ Create a WCS geometry object.
Pixelization of the map is set with
binsz
and one of eithernpix
orwidth
arguments. For maps with non-spatial dimensions a different pixelization can be used for each image plane by passing a list or array argument for any of the pixelization parameters. If both npix and width are None then an all-sky geometry will be created.- Parameters
- npixint or tuple or list
Width of the map in pixels. A tuple will be interpreted as parameters for longitude and latitude axes. For maps with non-spatial dimensions, list input can be used to define a different map width in each image plane. This option supersedes width.
- widthfloat or tuple or list
Width of the map in degrees. A tuple will be interpreted as parameters for longitude and latitude axes. For maps with non-spatial dimensions, list input can be used to define a different map width in each image plane.
- binszfloat or tuple or list
Map pixel size in degrees. A tuple will be interpreted as parameters for longitude and latitude axes. For maps with non-spatial dimensions, list input can be used to define a different bin size in each image plane.
- skydirtuple or
SkyCoord
Sky position of map center. Can be either a SkyCoord object or a tuple of longitude and latitude in deg in the coordinate system of the map.
- frame{“icrs”, “galactic”}, optional
Coordinate system, either Galactic (“galactic”) or Equatorial (“icrs”).
- axeslist
List of non-spatial axes.
- projstring, optional
Any valid WCS projection type. Default is ‘CAR’ (cartesian).
- refpixtuple
Reference pixel of the projection. If None this will be set to the center of the map.
- Returns
- geom
WcsGeom
A WCS geometry object.
- geom
Examples
>>> from gammapy.maps import WcsGeom >>> from gammapy.maps import MapAxis >>> axis = MapAxis.from_bounds(0,1,2) >>> geom = WcsGeom.create(npix=(100,100), binsz=0.1) >>> geom = WcsGeom.create(npix=[100,200], binsz=[0.1,0.05], axes=[axis]) >>> geom = WcsGeom.create(width=[5.0,8.0], binsz=[0.1,0.05], axes=[axis]) >>> geom = WcsGeom.create(npix=([100,200],[100,200]), binsz=0.1, axes=[axis])
-
crop
(crop_width)[source]¶ Crop the geometry at the edges.
- Parameters
- crop_width{sequence, array_like, int}
Number of values cropped from the edges of each axis.
- Returns
- geom
Geom
Cropped geometry.
- geom
-
cutout
(position, width, mode='trim')[source]¶ Create a cutout around a given position.
- Parameters
- Returns
- cutout
WcsNDMap
Cutout map
- cutout
-
downsample
(factor, axis_name=None)[source]¶ Downsample the spatial dimension of the geometry by a given factor.
- Parameters
- factorint
Downsampling factor.
- axis_namestr
Axis to downsample.
- Returns
- geom
Geom
Downsampled geometry.
- geom
-
drop
(axis_name)¶ Drop an axis from the geom.
- Parameters
- axis_namestr
Name of the axis to remove.
- Returns
- geom
Geom
New geom with the axis removed.
- geom
-
energy_mask
(energy_min=None, energy_max=None, round_to_edge=False)¶ Create a mask for a given energy range.
The energy bin must be fully contained to be included in the mask.
-
classmethod
from_hdulist
(hdulist, hdu=None, hdu_bands=None)¶ Load a geometry object from a FITS HDUList.
-
classmethod
from_header
(header, hdu_bands=None, format=None)[source]¶ Create a WCS geometry object from a FITS header.
- Parameters
- header
Header
The FITS header
- hdu_bands
BinTableHDU
The BANDS table HDU.
- format{‘gadf’, ‘fgst-ccube’,’fgst-template’}
FITS format convention.
- header
- Returns
- wcs
WcsGeom
WCS geometry object.
- wcs
-
get_coord
(idx=None, flat=False, mode='center', frame=None)[source]¶ Get map coordinates from the geometry.
- Parameters
- mode{‘center’, ‘edges’}
Get center or edge coordinates for the spatial axes.
- Returns
- coord
MapCoord
Map coordinate object.
- coord
-
get_idx
(idx=None, flat=False)[source]¶ Get tuple of pixel indices for this geometry.
Returns all pixels in the geometry by default. Pixel indices for a single image plane can be accessed by setting
idx
to the index tuple of a plane.- Parameters
- idxtuple, optional
A tuple of indices with one index for each non-spatial dimension. If defined only pixels for the image plane with this index will be returned. If none then all pixels will be returned.
- localbool
Flag to return local or global pixel indices. Local indices run from 0 to the number of pixels in a given image plane.
- flatbool, optional
Return a flattened array containing only indices for pixels contained in the geometry.
- Returns
- idxtuple
Tuple of pixel index vectors with one vector for each dimension.
-
get_pix
(idx=None, mode='center')[source]¶ Get map pix coordinates from the geometry.
- Parameters
- mode{‘center’, ‘edges’}
Get center or edge pix coordinates for the spatial axes.
- Returns
- coordtuple
Map pix coordinate tuple.
-
is_aligned
(other, tolerance=1e-06)[source]¶ Check if WCS and extra axes are aligned.
- Parameters
- other
WcsGeom
Other geom.
- tolerancefloat
Tolerance for the comparison.
- other
- Returns
- alignedbool
Whether geometries are aligned
-
pad
(pad_width)[source]¶ Pad the geometry at the edges.
- Parameters
- pad_width{sequence, array_like, int}
Number of values padded to the edges of each axis.
- Returns
- geom
Geom
Padded geometry.
- geom
-
pix_to_coord
(pix)[source]¶ Convert pixel coordinates to map coordinates.
- Parameters
- pixtuple
Tuple of pixel coordinates.
- Returns
- coordstuple
Tuple of map coordinates.
-
pix_to_idx
(pix, clip=False)[source]¶ Convert pixel coordinates to pixel indices.
Returns -1 for pixel coordinates that lie outside of the map.
- Parameters
- pixtuple
Tuple of pixel coordinates.
- clipbool
Choose whether to clip indices to the valid range of the geometry. If false then indices for coordinates outside the geometry range will be set -1.
- Returns
- idxtuple
Tuple of pixel indices.
-
region_mask
(regions, inside=True)[source]¶ Create a mask from a given list of regions
- Parameters
- regionslist of
Region
Python list of regions (pixel or sky regions accepted)
- insidebool
For
inside=True
, pixels in the region to True (the default). Forinside=False
, pixels in the region are False.
- regionslist of
- Returns
- mask_map
ndarray
of boolean type Boolean region mask
- mask_map
Examples
Make an exclusion mask for a circular region:
from regions import CircleSkyRegion from astropy.coordinates import SkyCoord, Angle from gammapy.maps import WcsNDMap, WcsGeom pos = SkyCoord(0, 0, unit='deg') geom = WcsGeom.create(skydir=pos, npix=100, binsz=0.1) region = CircleSkyRegion( SkyCoord(3, 2, unit='deg'), Angle(1, 'deg'), ) mask = geom.region_mask([region], inside=False)
Note how we made a list with a single region, since this method expects a list of regions.
The return
mask
is a boolean Numpy array. If you want a map object (e.g. for storing in FITS or plotting), this is how you can make the map:mask_map = WcsNDMap(geom=geom, data=mask) mask_map.plot()
-
resample_axis
(axis)¶ Resample geom to a new axis binning.
This method groups the existing bins into a new binning.
-
slice_by_idx
(slices)¶ Create a new geometry by slicing the non-spatial axes.
-
solid_angle
()[source]¶ Solid angle array (
Quantity
insr
).The array has the same dimension as the WcsGeom object.
To return solid angles for the spatial dimensions only use:
WcsGeom.to_image().solid_angle()
-
squash
(axis_name)¶ Squash geom axis.
- Parameters
- axis_namestr
Axis to squash.
- Returns
- geom
Geom
Geom with squashed axis.
- geom
-
to_bands_hdu
(hdu=None, hdu_skymap=None, format=None)¶
-
to_binsz
(binsz)[source]¶ Change pixel size of the geometry.
- Parameters
- binszfloat or tuple or list
New pixel size in degree.
- Returns
- geom
WcsGeom
Geometry with new pixel size.
- geom
-
to_cube
(axes)[source]¶ Append non-spatial axes to create a higher-dimensional geometry.
This will result in a new geometry with N+M dimensions where N is the number of current dimensions and M is the number of axes in the list.
- Parameters
- axeslist
Axes that will be appended to this geometry.
- Returns
- geom
Geom
Map geometry.
- geom