lsst.meas.algorithms ge6526c86ff+fde82a80b9
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Functions
lsst.meas.algorithms.variance_plane Namespace Reference

Functions

 remove_signal_from_variance (exposure, gain=None, gains=None, average_across_amps=False, in_place=False)
 

Detailed Description

Utility functions related to the variance plane of Exposure objects. Tested
in `ip_isr/tests/test_variance_plane.py` to avoid circular dependencies.

Function Documentation

◆ remove_signal_from_variance()

lsst.meas.algorithms.variance_plane.remove_signal_from_variance ( exposure,
gain = None,
gains = None,
average_across_amps = False,
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.