Image#

Bases: GeneralizedImage

A 2-d array that may be augmented with units and a nonzero origin.

Parameters#

array_or_fill: Array or fill value for the image. If a fill value, bbox or shape must be provided.
bbox: Bounding box for the image.
yx0: Logical coordinates of the first pixel in the array, ordered y, x (unless an XY instance is passed). Ignored if bbox is provided. Defaults to zeros.
shape: Leading dimensions of the array, ordered y, x (unless an XY instance is passed). Only needed if array_or_fill is not an array and bbox is not provided. Like the bbox, this does not include the last dimension of the array.
dtype: Pixel data type override.
unit: Units for the image’s pixel values.
sky_projection: Projection that maps the pixel grid to the sky.
metadata: Arbitrary flexible metadata to associate with the image.

Notes#

Indexing the array attribute of an Image does not take into account its yx0 offset, but accessing a subimage by indexing an Image with a Box does, and the bbox of the subimage is set to match its location within the original image.

Indexed assignment to a subimage requires consistency between the coordinate systems and units of both operands, but it will automatically select a subimage of the right-hand side and convert compatible units when possible. In other words:

a[box] = b

is a shortcut for

a[box].quantity = b[box].quantity

An ellipsis (...) can be used instead of a Box to assign to the full image.

Attributes Summary

`absolute`	A proxy object for slicing a generalized image using absolute pixel coordinates.
`array`	The low-level array (`numpy.ndarray`).
`astropy_wcs`	An Astropy WCS for this image's pixel array.
`bbox`	Bounding box for the image (`Box`).
`butler_dataset`	The butler dataset reference for this image (`lsst.daf.butler.SerializedDatasetRef` \| `None`).
`butler_provenance`	The butler inputs and ID of the task quantum that produced this dataset (`lsst.daf.butler.DatasetProvenance` \| `None`)
`fits_wcs`	An Astropy FITS WCS for this image's pixel array.
`local`	A proxy object for slicing a generalized image using "local" or "array" pixel coordinates.
`metadata`	Arbitrary flexible metadata associated with the image (`dict`).
`quantity`	The low-level array with units (`astropy.units.Quantity`).
`sky_projection`	The projection that maps this image's pixel grid to the sky (`SkyProjection` \| `None`).
`unit`	Units for the image's pixel values (`astropy.units.Unit` or `None`).
`yx0`	The coordinates of the first pixel in the array (`YX` [`int`]).

Methods Summary

`copy`()	Deep-copy the image and metadata.
`from_legacy`(legacy[, unit])	Convert from an `lsst.afw.image.Image` instance.
`read`(path, **kwargs)	Read an instance of this class from a file.
`read_legacy`(uri, *[, preserve_quantization, ...])	Read a FITS file written by `lsst.afw.image.Image.writeFits`.
`serialize`(archive, *[, update_header, ...])	Serialize the image to an output archive.
`to_legacy`(*[, copy])	Convert to an `lsst.afw.image.Image` instance.
`view`(*[, unit, sky_projection, yx0])	Make a view of the image, with optional updates.
`write`(path, **kwargs)	Write this object to a file.

Attributes Documentation

absolute#: A proxy object for slicing a generalized image using absolute pixel coordinates.

Notes#

In this convention, the first row and column of the pixel grid is bbox.start. A subimage and its parent image share the same absolute pixel coordinate system, and most lsst.images types (e.g. Box, SkyProjection, PointSpreadFunction) operate exclusively in this system.

Note that astropy.wcs and numpy.ndarray are not aware of the bbox.start offset that defines tihs coordinates system; use local slicing for indices obtained from those.

See Also#

lsst.images.BoxSliceFactory lsst.images.IntervalSliceFactory

array#

The low-level array (numpy.ndarray).

Assigning to this attribute modifies the existing array in place; the bounding box and underlying data pointer are never changed.

astropy_wcs#: An Astropy WCS for this image’s pixel array.

Notes#

As expected for Astropy WCS objects, this defines pixel coordinates such that the first row and column in any associated arrays are (0, 0), not bbox.start, as is the case for sky_projection.

This object satisfies the astropy.wcs.wcsapi.BaseHighLevelWCS and astropy.wcs.wcsapi.BaseLowLevelWCS interfaces, but it is not an astropy.wcs.WCS (use fits_wcs for that).

bbox#: Bounding box for the image (Box).

butler_dataset#: The butler dataset reference for this image (lsst.daf.butler.SerializedDatasetRef | None).

butler_provenance#: The butler inputs and ID of the task quantum that produced this dataset (lsst.daf.butler.DatasetProvenance | None)

fits_wcs#: An Astropy FITS WCS for this image’s pixel array.

Notes#

As expected for Astropy WCS objects, this defines pixel coordinates such that the first row and column in any associated arrays are (0, 0), not bbox.start, as is the case for sky_projection.

This may be an approximation or absent if sky_projection is not naturally representable as a FITS WCS.

local#: A proxy object for slicing a generalized image using “local” or “array” pixel coordinates.

Notes#

In this convention, the first row and column of the pixel grid is always at (0, 0). This is also the convention used by astropy.wcs objects. When a subimage is created from a parent image, its “local” coordinate system is offset from the coordinate systems of the parent image.

Note that most lsst.images types (e.g. Box, SkyProjection, PointSpreadFunction) operate instead in “absolute” coordinates, which is shared by subimage and their parents.

See Also#

lsst.images.BoxSliceFactory lsst.images.IntervalSliceFactory

metadata#: Arbitrary flexible metadata associated with the image (dict).

Notes#

Metadata is shared with subimages and other views. It can be disconnected by reassigning to a copy explicitly:

image.metadata = image.metadata.copy()

quantity#

The low-level array with units (astropy.units.Quantity).

Assigning to this attribute modifies the existing array in place; the bounding box and underlying data pointer are never changed.

sky_projection#: The projection that maps this image’s pixel grid to the sky (SkyProjection | None).

Notes#

The pixel coordinates used by this projection account for the bounding box start; they are not just array indices.

unit#: Units for the image’s pixel values (astropy.units.Unit or None).

yx0#: The coordinates of the first pixel in the array (YX [int]).

Methods Documentation

copy() → Image#

Deep-copy the image and metadata.

Attached immutable objects (like SkyProjection instances) are not copied.

static from_legacy(legacy: LegacyImage, unit: astropy.units.UnitBase | None = None) → Image#

Convert from an lsst.afw.image.Image instance.

Parameters#

legacy: An lsst.afw.image.Image instance that will share pixel data with

the returned object.
unit: Units of the image.

classmethod read(path: str | ParseResult | ResourcePath | Path, **kwargs: Any) → Self#

Read an instance of this class from a file.

A thin convenience wrapper around lsst.images.serialization.read that fixes the expected in-memory type to this class. The container format is inferred from path’s extension.

Parameters#

path: File to read; convertible to lsst.resources.ResourcePath.
**kwargs: Forwarded to read (e.g. bbox to read a subimage).

Read a FITS file written by lsst.afw.image.Image.writeFits.

Parameters#

uri: URI or file name.
preserve_quantization: If True, ensure that writing the image back out again will exactly preserve quantization-compressed pixel values. This causes the arrays to be marked as read-only and stores the original binary table data for those planes in memory. If the Image is copied, the precompressed pixel values are not transferred to the copy.
ext: Name or index of the FITS HDU to read.
fits_wcs_frame: If not None and the HDU containing the image has a FITS WCS, attach a SkyProjection to the returned image by converting that WCS.

serialize(archive: ~lsst.images.serialization._output_archive.OutputArchive, *, update_header: ~collections.abc.Callable[[~astropy.io.fits.header.Header], None] = <function no_header_updates>, save_projection: bool = True, add_offset_wcs: str | None = 'A', tile_shape: tuple[int, ...] | None = None, options_name: str | None = None) → ImageSerializationModel[TypeVar]#

Serialize the image to an output archive.

Parameters#

archive: Archive to write to.
update_header: A callback that will be given the FITS header for the HDU containing this image in order to add keys to it. This callback may be provided but will not be called if the output format is not FITS.
save_projection: If True, save the SkyProjection attached to the image, if there is one. This does not affect whether a FITS WCS corresponding to the projection is written (it always is, if available, and if add_offset_wcs is not " ").
add_offset_wcs: A FITS WCS single-character suffix to use when adding a linear WCS that maps the FITS array to the logical pixel coordinates defined by bbox.start. Set to None to not write this WCS. If this is set to " ", it will prevent the SkyProjection from being saved as a FITS WCS.
tile_shape: The recommended shape of each tile, if the archive will save the array in distinct tiles for faster subarray retrieval. This is a hint; archives are not required to use this value.
options_name: Use this name to look up archive options.

to_legacy(*, copy: bool | None = None) → LegacyImage#

Convert to an lsst.afw.image.Image instance.

Parameters#

copy: If True, always copy the pixel data. If False, return a view, and raise TypeError if the pixel data is read-only (this is not supported by afw). If None, onyl if the pixel data is read-only.

view(*, unit: UnitBase | None | ellipsis = Ellipsis, sky_projection: SkyProjection | None | ellipsis = Ellipsis, yx0: Sequence[int] | ellipsis = Ellipsis) → Image#: Make a view of the image, with optional updates.

write(path: str, **kwargs: Any) → None#

Write this object to a file.

A thin convenience wrapper around lsst.images.serialization.write. The container format is chosen from path’s extension.

Parameters#

path: Destination file path. Must not already exist.
**kwargs: Forwarded to write (e.g. compression_options and compression_seed for FITS).

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