Utility functions related to the variance plane of Exposure objects. Tested
in `ip_isr/tests/test_variance_plane.py` to avoid circular dependencies.
lsst.meas.algorithms.variance_plane.remove_signal_from_variance |
( |
| exposure, |
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| gain = None, |
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| gains = None, |
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| average_across_amps = False, |
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| in_place = False ) |
Removes the Poisson contribution from actual sources in the variance plane
of an Exposure.
If neither gain nor gains are provided, the function estimates the gain(s).
If ``average_across_amps`` is True, a single gain value for the entire
image is estimated. If False, individual gain values for each amplifier are
estimated. The estimation involves a linear fit of variance versus image
plane.
Parameters
----------
exposure : `~lsst.afw.image.Exposure`
The background-subtracted exposure containing a variance plane to be
corrected for source contributions.
gain : `float`, optional
The gain value for the entire image. This parameter is used if
``gains`` is not provided. If both ``gain`` and ``gains`` are None, and
``average_across_amps`` is True, ``gain`` is estimated from the image
and variance planes.
gains : dict[`str`, `float`], optional
A dictionary mapping amplifier ID (as a string) to gain value. This
parameter is used if ``gain`` is not provided. If both ``gain`` and
``gains`` are None, and ``average_across_amps`` is False, ``gains`` are
estimated from the image and variance planes.
average_across_amps : `bool`, optional
Determines the gain estimation strategy. If True, the gain for the
entire image is estimated at once. If False, individual gains for each
amplifier are estimated. This parameter is ignored if either ``gain``
or ``gains`` is specified.
in_place : `bool`, optional
If True, the variance plane of the input Exposure is modified in place.
A modified copy of the variance plane is always returned irrespective
of this.
Returns
-------
variance_plane : `~lsst.afw.image.Image`
The corrected variance plane, with the signal contribution removed.
Raises
------
AttributeError
If amplifiers cannot be retrieved from the exposure.
ValueError
If both ``gain`` and ``gains`` are provided, or if the number of
provided ``gains`` does not match the number of amplifiers.
Definition at line 31 of file variance_plane.py.