PiffWrapper#

class lsst.images.psfs.PiffWrapper(impl: piff.PSF, bounds: Bounds, stamp_size: int)#

Bases: PointSpreadFunction

A PSF model backed by the Piff library.

Parameters#

impl: The Piff PSF object to wrap.
bounds: The pixel-coordinate region where the model can safely be evaluated.
stamp_size: Side length in pixels of the PSF image stamps drawn by the model.

Attributes Summary

`bounds`	The region where this PSF model is valid.
`kernel_bbox`	Bounding box of all images returned by `compute_kernel_image`.
`piff_psf`	The backing `piff.PSF` object.

Methods Summary

`compute_kernel_image`(*, x, y)	Evaluate the PSF model into an image suitable for convolution.
`compute_stellar_bbox`(*, x, y)	Return the bounding box of the image that would be returned by `compute_stellar_image`.
`compute_stellar_image`(*, x, y)	Evaluate the PSF model into an image suitable for comparison with the image of an astrophysical point source.
`from_legacy`(legacy_psf, bounds)	Make a PSF object from a legacy `lsst.afw.detection.Psf` instance.
`serialize`(archive)	Serialize the PSF to an archive.
`to_legacy`()	Convert to a legacy `lsst.meas.extensions.piff.piffPsf`.

Attributes Documentation

bounds#

kernel_bbox#

piff_psf#

The backing piff.PSF object.

This is an internal object that must not be modified in place.

Methods Documentation

compute_kernel_image(*, x: float, y: float) → Image#

Evaluate the PSF model into an image suitable for convolution.

Parameters#

x: Column position coordinate to evaluate at.
y: Row position coordinate to evaluate at.

Returns#

Image: An image of the PSF, centered on the center of the center pixel, which is defined to be (0, 0) by the image’s origin.

compute_stellar_bbox(*, x: float, y: float) → Box#

Return the bounding box of the image that would be returned by compute_stellar_image.

Parameters#

x: Column position coordinate to evaluate at.
y: Row position coordinate to evaluate at.

Returns#

Box: The bounding box of the image that would be returned by compute_stellar_image at the given point.

compute_stellar_image(*, x: float, y: float) → Image#

Evaluate the PSF model into an image suitable for comparison with the image of an astrophysical point source.

Parameters#

x: Column position coordinate to evaluate at.
y: Row position coordinate to evaluate at.

Returns#

Image: An image of the PSF, centered on the given coordinates, just like the postage stamp of a star would be.

classmethod from_legacy(legacy_psf: LegacyPiffPsf, bounds: Bounds) → PiffWrapper#

Make a PSF object from a legacy lsst.afw.detection.Psf instance.

Parameters#

legacy_psf: Legacy PSF object.
bounds: The region where this PSF model is valid.

Returns#

PointSpreadFunction: The converted PSF object.

Notes#

This base class method is a factory dispatch function that automatically selects the right PointSpreadFunction subclass to use. When that is already known, a subclass from_legacy method can be called instead.

serialize(archive: OutputArchive[Any]) → PiffSerializationModel#

Serialize the PSF to an archive.

This method is intended to be usable as the callback function passed to serialization.OutputArchive.serialize_direct or serialization.OutputArchive.serialize_pointer.

Parameters#

archive: Archive to write to.

to_legacy() → LegacyPiffPsf#: Convert to a legacy lsst.meas.extensions.piff.piffPsf.