SplineField

final class lsst.images.fields.SplineField(bounds, data, *, y, x, unit=None)

Bases: BaseField

A 2-d Akima spline interpolation of data on a regular grid.

Parameters:

• bounds (Bounds) – The region where this field can be evaluated.

• data (ndarray) – The data points to be interpolated. Missing values (indicated by NaN) are allowed. Will be set to read-only in place.

• y (ndarray) – Coordinates for the first dimension of data. Will be set to read-only in place.

• x (ndarray) – Coordinates for the second dimension of data. Will be set to read-only in place.

• unit (UnitBase | None, default: None) – Units of the field.

Notes

This field is much faster to evaluate on a grid via render than at arbitrary points via the function-call operator.

Attributes Summary

bounds	The region over which this field can be evaluated (Bounds).
data	The data points to be interpolated (numpy.ndarray).
is_constant	Whether the field is spatially constant (bool).
unit	The units of the field (astropy.units.UnitBase or None).
x	Coordinates for the second dimension of data (numpy.ndarray).
y	Coordinates for the first dimension of data (numpy.ndarray).

Methods Summary

__call__([point, x, y, quantity])	Call self as a function.
from_legacy_background(legacy_background[, ...])	Convert from a legacy lsst.afw.math.BackgroundMI instance.
make_legacy_photo_calib(image_unit)	Make a legacy lsst.afw.image.PhotoCalib for an image with the given units, if that is possible without a photometric scaling field.
render([bbox, dtype])	Create an image realization of the field.
serialize(archive)	Serialize the spline field to an output archive.
to_legacy()	Convert to a legacy lsst.afw.math.BoundedField.
to_legacy_photo_calib(image_unit)	Convert to a legacy lsst.afw.image.PhotoCalib.

Attributes Documentation

bounds

data

The data points to be interpolated (numpy.ndarray).

May have missing values indicated by NaNs.

is_constant

unit

x

Coordinates for the second dimension of data (numpy.ndarray).

y

Coordinates for the first dimension of data (numpy.ndarray).

Methods Documentation

__call__(point=None, /, *, x=None, y=None, quantity=False)

Call self as a function.

Parameters:

• point (Union[XY[Any], YX[Any], None], default: None)

• x (Any, default: None)

• y (Any, default: None)

• quantity (bool, default: False)

Return type:

float | ndarray | Quantity

static from_legacy_background(legacy_background, bounds=None, unit=None)

Convert from a legacy lsst.afw.math.BackgroundMI instance.

Parameters:

• legacy_background (TypeAliasType) – Legacy background object to convert.

• bounds (Bounds | None, default: None) – The bounds of the returned field, if they should be different from the bounding box of legacy_background.

• unit (UnitBase | None, default: None) – The units of the returned field (lsst.afw.math.Background objects do not know their units).

Return type:

SplineField

Notes

SplineField.render and the lsst.afw background interpolator both use Akima splines, but with slightly different boundary conditions. They should produce equivalent to single-precision round-off error when evaluated within the region enclosed by bin centers (i.e. where no extrapolation is necessary) and when there are five or more points to be interpolated in each row and column.

static make_legacy_photo_calib(image_unit)

Make a legacy lsst.afw.image.PhotoCalib for an image with the given units, if that is possible without a photometric scaling field.

Parameters:

image_unit (UnitBase) – Units of the image the photometric calibration applies to.

Return type:

TypeAliasType | None

render(bbox=None, *, dtype=None)

Create an image realization of the field.

Parameters:

• bbox (Box | None, default: None) – Bounding box of the image. If not provided, self.bounds.bbox will be used.

• dtype (TypeAliasType | None, default: None) – Pixel data type for the returned image.

Return type:

Image

serialize(archive)

Serialize the spline field to an output archive.

Parameters:

archive (OutputArchive[Any]) – Archive to write to.

Return type:

SplineFieldSerializationModel

to_legacy()

Convert to a legacy lsst.afw.math.BoundedField.

Return type:

TypeAliasType

to_legacy_photo_calib(image_unit)

Convert to a legacy lsst.afw.image.PhotoCalib.

Parameters:

image_unit (UnitBase) – The units of the pixels the returned PhotoCalib will be associated with.

Return type:

TypeAliasType