Geom¶

class gammapy.maps.Geom[source]¶

Bases: abc.ABC

Map geometry base class.

See also: WcsGeom and HpxGeom

Attributes Summary

`as_energy_true`	If the geom contains an energy axis rename it to energy true
`center_coord`
`center_pix`
`center_skydir`
`data_shape`	Shape of the Numpy data array matching this geometry.
`has_energy_axis`	Whether geom has an energy axis
`is_allsky`
`is_flat`	Whether the geom non spatial axes have length 1, i.e.
`is_image`	Whether the geom is an image without extra dimensions.

Methods Summary

`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.
`crop`(crop_width)	Crop the geometry at the edges.
`data_nbytes`([dtype])	Estimate memory usage in megabytes of the Numpy data array matching this geometry depending on the given type.
`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.
`get_coord`([idx, flat])	Get the coordinate array for this geometry.
`get_idx`([idx, local, flat])	Get tuple of pixel indices for this geometry.
`pad`(pad_width, axis_name)	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.
`replace_axis`(axis)	Replace axis with a new one.
`resample_axis`(axis)	Resample geom to a new axis binning.
`slice_by_idx`(slices)	Create a new geometry by slicing the non-spatial axes.
`solid_angle`()	Solid angle (`Quantity` in `sr`).
`squash`(axis_name)	Squash geom axis.
`to_bands_hdu`([hdu_bands, format])
`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

center_coord¶

center_pix¶

center_skydir¶

data_shape¶: Shape of the Numpy data array matching this geometry.

has_energy_axis¶: Whether geom has an energy axis

is_allsky¶

is_flat¶: Whether the geom non spatial axes have length 1, i.e. if the geom is equivalent to an image.

is_image¶: Whether the geom is an image without extra dimensions.

Methods Documentation

abstract contains(coords)[source]¶

Check if a given map coordinate is contained in the geometry.

Parameters

coordstuple or MapCoord: Tuple of map coordinates.

Returns

containmentndarray: Bool array.

contains_pix(pix)[source]¶

Check if a given pixel coordinate is contained in the geometry.

Parameters

pixtuple: Tuple of pixel coordinates.

Returns

containmentndarray: Bool array.

coord_to_idx(coords, clip=False)[source]¶

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.

Returns

pixtuple: Tuple of pixel indices in image and band dimensions. Elements set to -1 correspond to coordinates outside the map.

abstract 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)[source]¶

Copy and overwrite given attributes.

Parameters

**kwargsdict: Keyword arguments to overwrite in the map geometry constructor.

Returns

copyGeom: Copied map geometry.

abstract 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

geomGeom: Cropped geometry.

data_nbytes(dtype='float32')[source]¶

Estimate memory usage in megabytes of the Numpy data array matching this geometry depending on the given type.

Parameters

dtypedata-type: The desired data-type for the array. Default is “float32”

Returns

memoryQuantity: Estimated memory usage in megabytes (MB)

abstract downsample(factor, axis_name)[source]¶

Downsample the spatial dimension of the geometry by a given factor.

Parameters

factorint: Downsampling factor.
axis_namestr: Axis to downsample.

Returns

geomGeom: Downsampled geometry.

drop(axis_name)[source]¶

Drop an axis from the geom.

Parameters

axis_namestr: Name of the axis to remove.

Returns

geomGeom: New geom with the axis removed.

energy_mask(energy_min=None, energy_max=None, round_to_edge=False)[source]¶

Create a mask for a given energy range.

The energy bin must be fully contained to be included in the mask.

Parameters

energy_min, energy_maxQuantity: Energy range

Returns

maskndarray: Energy mask

classmethod from_hdulist(hdulist, hdu=None, hdu_bands=None)[source]¶

Load a geometry object from a FITS HDUList.

Parameters

hdulistHDUList: HDU list containing HDUs for map data and bands.
hdustr: Name or index of the HDU with the map data.
hdu_bandsstr: Name or index of the HDU with the BANDS table. If not defined this will be inferred from the FITS header of the map HDU.

Returns

geomGeom: Geometry object.

abstract get_coord(idx=None, flat=False)[source]¶

Get the coordinate array for this geometry.

Returns a coordinate array with the same shape as the data array. Pixels outside the geometry are set to NaN. Coordinates 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 coordinates for the image plane with this index will be returned. If none then coordinates for all pixels will be returned.
flatbool, optional: Return a flattened array containing only coordinates for pixels contained in the geometry.

Returns

coordstuple: Tuple of coordinate vectors with one vector for each dimension.

abstract get_idx(idx=None, local=False, 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.

pad(pad_width, axis_name)[source]¶

Pad the geometry at the edges.

Parameters

pad_width{sequence, array_like, int}: Number of values padded to the edges of each axis.
axis_namestr: Name of the axis to pad.

Returns

geomGeom: Padded geometry.

abstract pix_to_coord(pix)[source]¶

Convert pixel coordinates to map coordinates.

Parameters

pixtuple: Tuple of pixel coordinates.

Returns

coordstuple: Tuple of map coordinates.

abstract 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.

replace_axis(axis)[source]¶

Replace axis with a new one.

Parameters

axisMapAxis: New map axis.

Returns

mapGeom: Geom with replaced axis.

resample_axis(axis)[source]¶

Resample geom to a new axis binning.

This method groups the existing bins into a new binning.

Parameters

axisMapAxis: New map axis.

Returns

mapGeom: Geom with resampled axis.

slice_by_idx(slices)[source]¶

Create a new geometry by slicing the non-spatial axes.

Parameters

slicesdict: Dict of axes names and integers or slice object pairs. Contains one element for each non-spatial dimension. For integer indexing the corresponding axes is dropped from the map. Axes not specified in the dict are kept unchanged.

Returns

geomGeom: Sliced geometry.

abstract solid_angle()[source]¶: Solid angle (Quantity in sr).

squash(axis_name)[source]¶

Squash geom axis.

Parameters

axis_namestr: Axis to squash.

Returns

geomGeom: Geom with squashed axis.

to_bands_hdu(hdu_bands=None, format='gadf')[source]¶

abstract 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

geomGeom: Map geometry.

abstract to_image()[source]¶

Create 2D image geometry (drop non-spatial dimensions).

Returns

geomGeom: Image geometry.

abstract upsample(factor, axis_name=None)[source]¶

Upsample the spatial dimension of the geometry by a given factor.

Parameters

factorint: Upsampling factor.
axis_namestr: Axis to upsample.

Returns

geomGeom: Upsampled geometry.