/usr/lib/python3/dist-packages/photutils/psf/funcs.py is in python3-photutils 0.4-1.
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"""
Models and functions for doing PSF/PRF fitting photometry on image data.
"""
from __future__ import division
import numpy as np
from astropy.table import Table
from astropy.nddata.utils import add_array, extract_array
__all__ = ['subtract_psf']
def _extract_psf_fitting_names(psf):
"""
Determine the names of the x coordinate, y coordinate, and flux from
a model. Returns (xname, yname, fluxname)
"""
if hasattr(psf, 'xname'):
xname = psf.xname
elif 'x_0' in psf.param_names:
xname = 'x_0'
else:
raise ValueError('Could not determine x coordinate name for '
'psf_photometry.')
if hasattr(psf, 'yname'):
yname = psf.yname
elif 'y_0' in psf.param_names:
yname = 'y_0'
else:
raise ValueError('Could not determine y coordinate name for '
'psf_photometry.')
if hasattr(psf, 'fluxname'):
fluxname = psf.fluxname
elif 'flux' in psf.param_names:
fluxname = 'flux'
else:
raise ValueError('Could not determine flux name for psf_photometry.')
return xname, yname, fluxname
def _call_fitter(fitter, psf, x, y, data, weights):
"""
Not all fitters have to support a weight array. This function
includes the weight in the fitter call only if really needed.
"""
if np.all(weights == 1.):
return fitter(psf, x, y, data)
else:
return fitter(psf, x, y, data, weights=weights)
def subtract_psf(data, psf, posflux, subshape=None):
"""
Subtract PSF/PRFs from an image.
Parameters
----------
data : `~astropy.nddata.NDData` or array (must be 2D)
Image data.
psf : `astropy.modeling.Fittable2DModel` instance
PSF/PRF model to be substracted from the data.
posflux : Array-like of shape (3, N) or `~astropy.table.Table`
Positions and fluxes for the objects to subtract. If an array,
it is interpreted as ``(x, y, flux)`` If a table, the columns
'x_fit', 'y_fit', and 'flux_fit' must be present.
subshape : length-2 or None
The shape of the region around the center of the location to
subtract the PSF from. If None, subtract from the whole image.
Returns
-------
subdata : same shape and type as ``data``
The image with the PSF subtracted
"""
if data.ndim != 2:
raise ValueError('{0}-d array not supported. Only 2-d arrays can be '
'passed to subtract_psf.'.format(data.ndim))
# translate array input into table
if hasattr(posflux, 'colnames'):
if 'x_fit' not in posflux.colnames:
raise ValueError('Input table does not have x_fit')
if 'y_fit' not in posflux.colnames:
raise ValueError('Input table does not have y_fit')
if 'flux_fit' not in posflux.colnames:
raise ValueError('Input table does not have flux_fit')
else:
posflux = Table(names=['x_fit', 'y_fit', 'flux_fit'], data=posflux)
# Set up contstants across the loop
psf = psf.copy()
xname, yname, fluxname = _extract_psf_fitting_names(psf)
indices = np.indices(data.shape)
subbeddata = data.copy()
if subshape is None:
indicies_reversed = indices[::-1]
for row in posflux:
getattr(psf, xname).value = row['x_fit']
getattr(psf, yname).value = row['y_fit']
getattr(psf, fluxname).value = row['flux_fit']
subbeddata -= psf(*indicies_reversed)
else:
for row in posflux:
x_0, y_0 = row['x_fit'], row['y_fit']
y = extract_array(indices[0], subshape, (y_0, x_0))
x = extract_array(indices[1], subshape, (y_0, x_0))
getattr(psf, xname).value = x_0
getattr(psf, yname).value = y_0
getattr(psf, fluxname).value = row['flux_fit']
subbeddata = add_array(subbeddata, -psf(x, y), (y_0, x_0))
return subbeddata
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