def to_odd_npix(self, max_radius=None):
"""Create a new geom object with an odd number of pixel and a maximum size.
This is useful for PSF kernel creation.
Parameters
----------
max_radius : `~astropy.units.Quantity`
Max. radius of the geometry (half the width)
Returns
-------
geom : `WcsGeom`
Geom with odd number of pixels
"""
if max_radius is None:
width = self.width.max()
else:
width = 2 * u.Quantity(max_radius)
binsz = self.pixel_scales.max()
width_npix = (width / binsz).to_value("")
npix = round_up_to_odd(width_npix)
return WcsGeom.create(
skydir=self.center_skydir,
binsz=binsz,
npix=npix,
proj=self.projection,
frame=self.frame,
axes=self.axes,
)
def cutout(self, position, width, mode="trim", odd_npix=False):
"""
Create a cutout around a given position.
Parameters
----------
position : `~astropy.coordinates.SkyCoord`
Center position of the cutout region.
width : tuple of `~astropy.coordinates.Angle`
Angular sizes of the region in (lon, lat) in that specific order.
If only one value is passed, a square region is extracted.
mode : {'trim', 'partial', 'strict'}
Mode option for Cutout2D, for details see `~astropy.nddata.utils.Cutout2D`.
odd_npix : bool
Force width to odd number of pixels.
Returns
-------
cutout : `~gammapy.maps.WcsNDMap`
Cutout map
"""
width = _check_width(width) * u.deg
binsz = self.pixel_scales
width_npix = np.clip((width / binsz).to_value(""), 1, None)
width = width_npix*binsz
if odd_npix:
width = round_up_to_odd(width_npix)
dummy_data = np.empty(self.to_image().data_shape)
c2d = Cutout2D(
data=dummy_data,
wcs=self.wcs,
position=position,
# Cutout2D takes size with order (lat, lon)
size=width[::-1],
mode=mode,
)
return self._init_copy(wcs=c2d.wcs, npix=c2d.shape[::-1])
def binary_structure(self, width, kernel="disk"):
"""Get binary structure
Parameters
----------
width : `~astropy.units.Quantity`, str or float
If a float is given it interpreted as width in pixels. If an (angular)
quantity is given it converted to pixels using ``geom.wcs.wcs.cdelt``.
The width corresponds to radius in case of a disk kernel, and
the side length in case of a box kernel.
kernel : {'disk', 'box'}
Kernel shape
Returns
-------
structure : `~numoy.ndarray`
Binary structure
"""
width = u.Quantity(width)
if width.unit.is_equivalent("deg"):
width = width / self.pixel_scales
width = round_up_to_odd(width.to_value(""))
if kernel == "disk":
disk = Tophat2DKernel(width[0])
disk.normalize("peak")
structure = disk.array
elif kernel == "box":
structure = np.ones(width)
else:
raise ValueError(f"Invalid kernel: {kernel!r}")
shape = (1, ) * len(self.axes) + structure.shape
return structure.reshape(shape)
