VisitImage#

class lsst.images.VisitImage(image: Image, *, mask: Mask | None = None, variance: Image | None = None, mask_schema: MaskSchema | None = None, projection: Projection[DetectorFrame] | None = None, bounds: Bounds | None = None, obs_info: ObservationInfo | None = None, summary_stats: ObservationSummaryStats | None = None, photometric_scaling: Field | None = None, psf: PointSpreadFunction | ArchiveReadError, detector: Detector, aperture_corrections: ApertureCorrectionMap | None = None, backgrounds: BackgroundMap | None = None, metadata: dict[str, MetadataValue] | None = None)#

Bases: MaskedImage

A calibrated single-visit image.

Parameters#

image: The main image plane. If this has a Projection, it will be used for all planes unless a projection is passed separately.
mask: A bitmask image that annotates the main image plane. Must have the same bounding box as image if provided. Any attached projection is replaced (possibly by None).
variance: The per-pixel uncertainty of the main image as an image of variance values. Must have the same bounding box as image if provided, and its units must be the square of image.unit or None. Values default to 1.0. Any attached projection is replaced (possibly by None).
mask_schema: Schema for the mask plane. Must be provided if and only if mask is not provided.
projection: Projection that maps the pixel grid to the sky. Can only be None if a projection is already attached to image.
bounds: The region where this image’s pixels and other properties are valid. If not provided, the bounding box of the image is used. Other components (psf, projection, aperture_corrections, etc.) are assumed to have their own bounds which may or may not be the same as the image bounds. If bounds extends beyond the image bounding box, the intersection between bounds and the image bounding box is used instead.
obs_info: General information about this visit in standardized form.
summary_stats: Summary statistics associated with this visit. Initialized to default values if not provided.
photometric_scaling: Field that can be used to multiply a post-ISR image units to yield calibrated image units. This may be a scaling that was already applied (so dividing by it will recover the post-ISR units) or a scaling that has not been applied, depending on image.unit.
psf: Point-spread function model for this image, or an exception explaining why it could not be read (to be raised if the PSF is requested later).
detector: Geometry and electronic information for the detector attached to this image.
aperture_correctionsdict [str, BaseField]: Mapping from photometry algorithm name to the aperture correction for that algorithm.
backgrounds: Background models associated with this image.
metadata: Arbitrary flexible metadata to associate with the image.

Attributes Summary

`absolute`	A proxy object for slicing a generalized image using absolute pixel coordinates.
`aperture_corrections`	A mapping from photometry algorithm name to the aperture correction field for that algorithm (`dict` [`str`, `BaseField`]).
`astropy_wcs`	An Astropy WCS for the pixel arrays (`ProjectionAstropyView`).
`backgrounds`	A mapping of backgrounds associated with this image (`BackgroundMap`).
`bbox`	The bounding box shared by all three image planes (`Box`).
`bounds`	The region where pixels are valid (`Bounds`).
`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`)
`detector`	Geometry and electronic information about the detector (`cameras.Detector`).
`fits_wcs`	An Astropy FITS WCS for this image's pixel array.
`image`	The main image plane (`Image`).
`local`	A proxy object for slicing a generalized image using "local" or "array" pixel coordinates.
`mask`	The mask plane (`Mask`).
`metadata`	Arbitrary flexible metadata associated with the image (`dict`).
`obs_info`	General information about this observation in standard form.
`photometric_scaling`	Field that multiplies a post-ISR image to yield the calibrated image (~`fields.BaseField`).
`projection`	The projection that maps the pixel grid to the sky (`Projection` [`DetectorFrame`]).
`psf`	The point-spread function model for this image (`psfs.PointSpreadFunction`).
`summary_stats`	Optional summary statistics for this observation (`ObservationSummaryStats`).
`unit`	The units of the image plane (`astropy.units.Unit`).
`variance`	The variance plane (`Image`).

Methods Summary

`convert_unit`([unit, copy, copy_detector])	Return an equivalent image with different pixel units.
`copy`(*[, copy_detector])	Deep-copy the visit image.
`from_legacy`(legacy, *[, unit, plane_map, ...])	Convert from an `lsst.afw.image.Exposure` instance.
`read_fits`(url, *[, bbox])	Read an image from a FITS file.
`read_legacy`()	Read a FITS file written by `lsst.afw.image.Exposure.writeFits`.
`serialize`(archive)	Serialize the masked image to an output archive.
`to_legacy`(*[, copy, plane_map])	Convert to an `lsst.afw.image.MaskedImage` instance.
`write_fits`(filename, *[, image_compression, ...])	Write the image to a FITS 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, Projection, 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

aperture_corrections#: A mapping from photometry algorithm name to the aperture correction field for that algorithm (dict [str, BaseField]).

astropy_wcs#: An Astropy WCS for the pixel arrays (ProjectionAstropyView).

Notes#

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

backgrounds#: A mapping of backgrounds associated with this image (BackgroundMap).

bbox#: The bounding box shared by all three image planes (Box).

bounds#: The region where pixels are valid (Bounds).

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)

detector#: Geometry and electronic information about the detector (cameras.Detector).

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 projection.

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

image#: The main image plane (Image).

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, Projection, PointSpreadFunction) operate instead in “absolute” coordinates, which is shared by subimage and their parents.

See Also#

lsst.images.BoxSliceFactory lsst.images.IntervalSliceFactory

mask#: The mask plane (Mask).

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()

obs_info#: General information about this observation in standard form. (ObservationInfo).

photometric_scaling#: Field that multiplies a post-ISR image to yield the calibrated image (~`fields.BaseField`).

projection#: The projection that maps the pixel grid to the sky (Projection [DetectorFrame]).

psf#: The point-spread function model for this image (psfs.PointSpreadFunction).

summary_stats#: Optional summary statistics for this observation (ObservationSummaryStats).

unit#: The units of the image plane (astropy.units.Unit).

variance#: The variance plane (Image).

Methods Documentation

convert_unit(unit: UnitBase = Unit('nJy'), copy: Literal['as-needed'] | bool = True, copy_detector: bool = False) → VisitImage#

Return an equivalent image with different pixel units.

Parameters#

unit

The unit to transform to. This may be any of the following:

any unit directly relatable to the current units via Astropy;
any unit relatable to the product of the current units with the photometric_scaling (i.e. if the current image is in instrumental units but we know how to calibrate them)
any unit relatable to the quotient of the current units with the photometric_scaling (i.e. if the current image is in calibrated units and we want to revert back to instrumental units).

copy

Whether to copy the images and other components. If True, all components that aren’t controlled by some other argument will always be deep-copied. If False, the operation will fail if the image is not already in the right units. If as-needed, only the image and variance will be copied, and only if they are not already in the right units.

copy_detector

Whether to deep-copy the detector attribute.

Returns#

VisitImage: An image with the given units.

copy(*, copy_detector: bool = False) → VisitImage#

Deep-copy the visit image.

Parameters#

copy_detector: Whether to deep-copy the detector attribute.

static from_legacy(legacy: Any, *, unit: UnitBase | None = None, plane_map: Mapping[str, MaskPlane] | None = None, instrument: str | None = None, visit: int | None = None) → VisitImage#

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

Parameters#

legacy: An lsst.afw.image.Exposure instance that will share image and variance (but not mask) pixel data with the returned object.
unit: Units of the image. If not provided, the BUNIT metadata key will be used, if available.
plane_map: A mapping from legacy mask plane name to the new plane name and description. If None (default) get_legacy_visit_image_mask_planes is used.
instrument: Name of the instrument. Extracted from the metadata if not provided.
visit: ID of the visit. Extracted from the metadata if not provided.

classmethod read_fits(url: str | ParseResult | ResourcePath | Path, *, bbox: Box | None = None) → MaskedImage#

Read an image from a FITS file.

Parameters#

url: URL of the file to read; may be any type supported by lsst.resources.ResourcePath.
bbox: Bounding box of a subimage to read instead.

static read_legacy(filename: str, *, component: Literal['bbox']) → Box#

static read_legacy(filename: str, *, preserve_quantization: bool = False, instrument: str | None = None, visit: int | None = None, component: Literal['image']) → Image

static read_legacy(filename: str, *, plane_map: Mapping[str, MaskPlane] | None = None, instrument: str | None = None, visit: int | None = None, component: Literal['mask']) → Mask

static read_legacy(filename: str, *, preserve_quantization: bool = False, instrument: str | None = None, visit: int | None = None, component: Literal['variance']) → Image

static read_legacy(filename: str, *, instrument: str | None = None, visit: int | None = None, component: Literal['projection']) → Projection[DetectorFrame]

static read_legacy(filename: str, *, component: Literal['psf']) → PointSpreadFunction

static read_legacy(filename: str, *, component: Literal['detector']) → Detector

static read_legacy(filename: str, *, component: Literal['obs_info']) → ObservationInfo

static read_legacy(filename: str, *, component: Literal['photometric_scaling']) → Field | None

static read_legacy(filename: str, *, component: Literal['summary_stats']) → ObservationSummaryStats

static read_legacy(filename: str, *, component: Literal['aperture_corrections']) → ApertureCorrectionMap

static read_legacy(filename: str, *, preserve_quantization: bool = False, plane_map: Mapping[str, MaskPlane] | None = None, instrument: str | None = None, visit: int | None = None, component: None = None) → VisitImage

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

Parameters#

filename: Full name of the file.
preserve_quantization: If True, ensure that writing the masked image back out again will exactly preserve quantization-compressed pixel values. This causes the image and variance plane arrays to be marked as read-only and stores the original binary table data for those planes in memory. If the MaskedImage is copied, the precompressed pixel values are not transferred to the copy.
plane_map: A mapping from legacy mask plane name to the new plane name and description. If None (default) get_legacy_visit_image_mask_planes is used.
instrument: Name of the instrument. Read from the primary header if not provided.
visit: ID of the visit. Read from the primary header if not provided.
component: A component to read instead of the full image.

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

Serialize the masked image to an output archive.

Parameters#

archive: Archive to write to.

to_legacy(*, copy: bool | None = None, plane_map: Mapping[str, MaskPlane] | None = None) → Any#

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

Parameters#

copy: If True, always copy the image and variance 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. Mask pixel data is always copied.
plane_map: A mapping from legacy mask plane name to the new plane name and description.

write_fits(filename: str, *, image_compression: ~lsst.images.fits._common.FitsCompressionOptions | None = FitsCompressionOptions(algorithm=<FitsCompressionAlgorithm.GZIP_2: 'GZIP_2'>, tile_shape=None, quantization=None), mask_compression: ~lsst.images.fits._common.FitsCompressionOptions | None = FitsCompressionOptions(algorithm=<FitsCompressionAlgorithm.GZIP_2: 'GZIP_2'>, tile_shape=None, quantization=None), variance_compression: ~lsst.images.fits._common.FitsCompressionOptions | None = FitsCompressionOptions(algorithm=<FitsCompressionAlgorithm.GZIP_2: 'GZIP_2'>, tile_shape=None, quantization=None), compression_seed: int | None = None) → None#

Write the image to a FITS file.

Parameters#

filename: Name of the file to write to. Must be a local file.
image_compression: Compression options for the image plane.
mask_compression: Compression options for the mask plane.
variance_compression: Compression options for the variance plane.
compression_seed: A FITS tile compression seed to use whenever the configured compression seed is None or (for backwards compatibility) 0. This value is then incremented every time it is used.

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