lsst.ip.diffim.dcrModel Namespace Reference

Classes
class	DcrModel

Functions
def	applyDcr (image, dcr, useInverse=False, splitSubfilters=False, splitThreshold=0., doPrefilter=True, order=3)
def	calculateDcr (visitInfo, wcs, filterInfo, dcrNumSubfilters, splitSubfilters=False)
def	calculateImageParallacticAngle (visitInfo, wcs)
def	wavelengthGenerator (filterInfo, dcrNumSubfilters)

Function Documentation

applyDcr()

def lsst.ip.diffim.dcrModel.applyDcr	(		image,
			dcr,
			useInverse = False,
			splitSubfilters = False,
			splitThreshold = 0.,
			doPrefilter = True,
			order = 3
	)

Shift an image along the X and Y directions.

Parameters
----------
image : `numpy.ndarray`
    The input image to shift.
dcr : `tuple`
    Shift calculated with ``calculateDcr``.
    Uses numpy axes ordering (Y, X).
    If ``splitSubfilters`` is set, each element is itself a `tuple`
    of two `float`, corresponding to the DCR shift at the two wavelengths.
    Otherwise, each element is a `float` corresponding to the DCR shift at
    the effective wavelength of the subfilter.
useInverse : `bool`, optional
    Apply the shift in the opposite direction. Default: False
splitSubfilters : `bool`, optional
    Calculate DCR for two evenly-spaced wavelengths in each subfilter,
    instead of at the midpoint. Default: False
splitThreshold : `float`, optional
    Minimum DCR difference within a subfilter required to use ``splitSubfilters``
doPrefilter : `bool`, optional
    Spline filter the image before shifting, if set. Filtering is required,
    so only set to False if the image is already filtered.
    Filtering takes ~20% of the time of shifting, so if `applyDcr` will be
    called repeatedly on the same image it is more efficient to precalculate
    the filter.
order : `int`, optional
    The order of the spline interpolation, default is 3.

Returns
-------
shiftedImage : `numpy.ndarray`
    A copy of the input image with the specified shift applied.

Definition at line 585 of file dcrModel.py.

calculateDcr()

def lsst.ip.diffim.dcrModel.calculateDcr	(		visitInfo,
			wcs,
			filterInfo,
			dcrNumSubfilters,
			splitSubfilters = False
	)

Calculate the shift in pixels of an exposure due to DCR.

Parameters
----------
visitInfo : `lsst.afw.image.VisitInfo`
    Metadata for the exposure.
wcs : `lsst.afw.geom.SkyWcs`
    Coordinate system definition (wcs) for the exposure.
filterInfo : `lsst.afw.image.Filter`
    The filter definition, set in the current instruments' obs package.
dcrNumSubfilters : `int`
    Number of sub-filters used to model chromatic effects within a band.
splitSubfilters : `bool`, optional
    Calculate DCR for two evenly-spaced wavelengths in each subfilter,
    instead of at the midpoint. Default: False

Returns
-------
dcrShift : `tuple` of two `float`
    The 2D shift due to DCR, in pixels.
    Uses numpy axes ordering (Y, X).

Definition at line 649 of file dcrModel.py.

calculateImageParallacticAngle()

def lsst.ip.diffim.dcrModel.calculateImageParallacticAngle	(		visitInfo,
			wcs
	)

Calculate the total sky rotation angle of an exposure.

Parameters
----------
visitInfo : `lsst.afw.image.VisitInfo`
    Metadata for the exposure.
wcs : `lsst.afw.geom.SkyWcs`
    Coordinate system definition (wcs) for the exposure.

Returns
-------
`lsst.geom.Angle`
    The rotation of the image axis, East from North.
    Equal to the parallactic angle plus any additional rotation of the
    coordinate system.
    A rotation angle of 0 degrees is defined with
    North along the +y axis and East along the +x axis.
    A rotation angle of 90 degrees is defined with
    North along the +x axis and East along the -y axis.

Definition at line 703 of file dcrModel.py.

wavelengthGenerator()

def lsst.ip.diffim.dcrModel.wavelengthGenerator	(		filterInfo,
			dcrNumSubfilters
	)

Iterate over the wavelength endpoints of subfilters.

Parameters
----------
filterInfo : `lsst.afw.image.Filter`
    The filter definition, set in the current instruments' obs package.
dcrNumSubfilters : `int`
    Number of sub-filters used to model chromatic effects within a band.

Yields
------
`tuple` of two `float`
    The next set of wavelength endpoints for a subfilter, in nm.

Definition at line 735 of file dcrModel.py.