Source code for gammapy.background.fov

# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""Field-of-view (FOV) background estimation."""
from __future__ import absolute_import, division, print_function, unicode_literals
import numpy as np
from astropy.wcs import WCS
from astropy.coordinates import Angle
from ..image import SkyImage

__all__ = [
    'fill_acceptance_image',
]


[docs]def fill_acceptance_image(header, center, offset, acceptance, offset_max=Angle(2.5, "deg"), offset_min=Angle(0.0, "deg"), interp_kwargs=None): """Generate a 2D image of a radial acceptance curve. The radial acceptance curve is given as an array of values defined at the specified offsets. Parameters ---------- header : `~astropy.io.fits.Header` Fits header of the reference image center : `~astropy.coordinates.SkyCoord` Coordinate of the center of the image. offset : `~astropy.coordinates.Angle` 1D array of offset values where acceptance is defined. acceptance : `~numpy.ndarray` Array of acceptance values. interp_kwargs : dict option for interpolation for `~scipy.interpolate.interp1d` Returns ------- image : `~astropy.io.fits.ImageHDU` New image filled with radial acceptance. """ from scipy.interpolate import interp1d if offset_max > Angle(offset)[-1]: raise ValueError('Offset max used for the acceptance curve ({} deg) is ' 'inferior to the one you asked to fill the map ({} deg)' ''.format(offset[-1], offset_max.value)) if not interp_kwargs: interp_kwargs = dict(bounds_error=False, fill_value=acceptance[0]) # initialize WCS to the header of the image wcs = WCS(header) data = np.zeros((header["NAXIS2"], header["NAXIS1"])) image = SkyImage(data=data, wcs=wcs) # calculate pixel offset from center (in world coordinates) coord = image.coordinates() pix_off = coord.separation(center) model = interp1d(offset, acceptance, kind='cubic', **interp_kwargs) image.data += model(pix_off) image.data[pix_off >= offset_max] = 0 image.data[pix_off <= offset_min] = 0 # TODO: return SkyImage here and adapt callers. return image.to_image_hdu()