Coverage for python / lsst / images / psfs / _piff.py: 37%
176 statements
« prev ^ index » next coverage.py v7.14.0, created at 2026-05-15 01:53 -0700
1# This file is part of lsst-images.
2#
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (https://www.lsst.org).
6# See the COPYRIGHT file at the top-level directory of this distribution
7# for details of code ownership.
8#
9# Use of this source code is governed by a 3-clause BSD-style
10# license that can be found in the LICENSE file.
12from __future__ import annotations
14from lsst.images.serialization import ArchiveReadError
16__all__ = ("PiffSerializationModel", "PiffWrapper")
18import operator
19from collections.abc import Iterator
20from contextlib import contextmanager
21from functools import cached_property
22from logging import getLogger
23from typing import TYPE_CHECKING, Annotated, Any, Literal
25import astropy.io.fits
26import numpy as np
27import pydantic
29from .. import serialization
30from .._concrete_bounds import SerializableBounds
31from .._geom import Bounds, Box
32from .._image import Image
33from ..utils import round_half_up
34from ._base import PointSpreadFunction
36if TYPE_CHECKING:
37 import galsim.wcs
38 import piff.config
40_LOG = getLogger(__name__)
43class PiffWrapper(PointSpreadFunction):
44 """A PSF model backed by the Piff library.
46 Parameters
47 ----------
48 impl
49 The Piff PSF object to wrap.
50 bounds
51 The pixel-coordinate region where the model can safely be evaluated.
52 """
54 def __init__(self, impl: piff.PSF, bounds: Bounds, stamp_size: int):
55 self._impl = impl
56 self._bounds = bounds
57 self._stamp_size = stamp_size
59 @property
60 def bounds(self) -> Bounds:
61 return self._bounds
63 @cached_property
64 def kernel_bbox(self) -> Box:
65 r = self._stamp_size // 2
66 return Box.factory[-r : r + 1, -r : r + 1]
68 def compute_kernel_image(self, *, x: float, y: float) -> Image:
69 if "colorValue" in self._impl.interp_property_names:
70 raise NotImplementedError("Chromatic PSFs are not yet supported.")
71 gs_image = self._impl.draw(x, y, stamp_size=self._stamp_size, center=True)
72 r = self._stamp_size // 2
73 result = Image(gs_image.array.copy(), start=(-r, -r))
74 result.array /= np.sum(result.array)
75 return result
77 def compute_stellar_image(self, *, x: float, y: float) -> Image:
78 if "colorValue" in self._impl.interp_property_names:
79 raise NotImplementedError("Chromatic PSFs are not yet supported.")
80 gs_image = self._impl.draw(x, y, stamp_size=self._stamp_size, center=None)
81 r = self._stamp_size // 2
82 result = Image(gs_image.array.copy(), start=(round_half_up(y) - r, round_half_up(x) - r))
83 result.array /= np.sum(result.array)
84 return result
86 def compute_stellar_bbox(self, *, x: float, y: float) -> Box:
87 r = self._stamp_size // 2
88 xi = round_half_up(x)
89 yi = round_half_up(y)
90 return Box.factory[yi - r : yi + r + 1, xi - r : xi + r + 1]
92 @property
93 def piff_psf(self) -> Any:
94 """The backing `piff.PSF` object.
96 This is an internal object that must not be modified in place.
97 """
98 return self._impl
100 @classmethod
101 def from_legacy(cls, legacy_psf: Any, bounds: Bounds) -> PiffWrapper:
102 return cls(impl=legacy_psf._piffResult, bounds=bounds, stamp_size=int(legacy_psf.width))
104 def serialize(self, archive: serialization.OutputArchive[Any]) -> PiffSerializationModel:
105 """Serialize the PSF to an archive.
107 This method is intended to be usable as the callback function passed to
108 `.serialization.OutputArchive.serialize_direct` or
109 `.serialization.OutputArchive.serialize_pointer`.
110 """
111 from piff.config import PiffLogger
113 writer = _ArchivePiffWriter()
114 with self._without_stars():
115 self._impl._write(writer, "piff", PiffLogger(_LOG))
116 piff_model = writer.serialize(archive)
117 return PiffSerializationModel(
118 piff=piff_model,
119 stamp_size=self._stamp_size,
120 bounds=self._bounds.serialize(),
121 )
123 @staticmethod
124 def _get_archive_tree_type(
125 pointer_type: type[pydantic.BaseModel],
126 ) -> type[PiffSerializationModel]:
127 """Return the serialization model type for this object for an archive
128 type that uses the given pointer type.
129 """
130 return PiffSerializationModel
132 @contextmanager
133 def _without_stars(self) -> Iterator[None]:
134 """Temporarily drop the embedded list of stars used to fit the PSF.
136 Notes
137 -----
138 By default Piff saves the list of stars (including postage stamps) used
139 to fit the PSF, which makes the serialized form much larger. But the
140 upstream Piff serialization code recognizes the case where that
141 ``stars`` attribute has been deleted and serializes everything else.
143 Unfortunately, to date, Rubin's pickle-based Piff serialization instead
144 just deletes the postage stamp image attributes from inside the Piff
145 ``stars`` list, which is not a state the Piff serialization code
146 handles gracefully. So for now we have to drop the full stars list
147 during serialization if it is present.
148 """
149 if hasattr(self._impl, "stars"):
150 stars = self._impl.stars
151 try:
152 del self._impl.stars
153 yield
154 finally:
155 self._impl.stars = stars
156 else:
157 yield
160# Conventions on public visibility of the serialization types:
161#
162# - We lift and document the outermost Pydantic model type, since that needs to
163# be included directly in the Pydantic models of types that hold a PSF. This
164# type needs to be very clearly documented and named as a *serialization*
165# model, since there are many other kinds of models in play in this package.
166#
167# - We do not lift or document types used in that outermost model, but we do
168# not give them leading underscores, since they aren't really private.
169#
170# - Other utility types do get leading underscores.
173# Piff serialization uses a lot of dictionaries and lists restricted to these
174# basic types.
175type PiffScalar = int | float | str | bool | None
176type PiffDict = dict[str, PiffScalar | list[PiffScalar]]
179class GalSimPixelScaleModel(pydantic.BaseModel, ser_json_inf_nan="constants"):
180 """Model used to serialize `galsim.wcs.PixelScale` instances."""
182 scale: float
183 wcs_type: Literal["pixel_scale"] = "pixel_scale"
186# We expect this discriminated union to grow to include other trivial
187# pixel-to-pixel transforms that get embedded in PSFs. If we someday have to
188# store Piff objects that embed more sophisticated PSFs, we'll hook them into
189# the AST-based coordinate transform system instead, but as long as we're just
190# talking about simple offsets and scalings, that's a lot of extra complexity
191# for very little gain.
192type GalSimLocalWcsModel = Annotated[GalSimPixelScaleModel, pydantic.Field(discriminator="wcs_type")]
195class PiffTableModel(pydantic.BaseModel, ser_json_inf_nan="constants"):
196 """Serialization model used to embed a reference to a binary-data table in
197 a Piff serialization's JSON-like data.
198 """
200 metadata: PiffDict
201 table: serialization.TableModel
204class PiffObjectModel(pydantic.BaseModel, ser_json_inf_nan="constants"):
205 """General-purpose serialization model used for various Piff objects."""
207 structs: dict[str, PiffDict] = pydantic.Field(default_factory=dict, exclude_if=operator.not_)
208 tables: dict[str, PiffTableModel] = pydantic.Field(default_factory=dict, exclude_if=operator.not_)
209 wcs: dict[str, GalSimLocalWcsModel] = pydantic.Field(default_factory=dict, exclude_if=operator.not_)
210 objects: dict[str, PiffObjectModel] = pydantic.Field(default_factory=dict, exclude_if=operator.not_)
213class PiffSerializationModel(serialization.ArchiveTree):
214 """Serialization model for a Piff PSF."""
216 piff: PiffObjectModel = pydantic.Field(description="The Piff PSF object itself.")
218 stamp_size: int = pydantic.Field(
219 description="Width of the (square) images returned by this PSF's methods."
220 )
222 bounds: SerializableBounds = pydantic.Field(
223 description="The bounds object that represents the PSF's validity region."
224 )
226 def deserialize(self, archive: serialization.InputArchive[Any]) -> PiffWrapper:
227 """Deserialize the PSF from an archive.
229 This method is intended to be usable as the callback function passed to
230 `.serialization.InputArchive.deserialize_pointer`.
231 """
232 try:
233 from piff import PSF
234 from piff.config import PiffLogger
235 except ImportError:
236 raise ArchiveReadError("Failed to import piff.") from None
238 reader = _ArchivePiffReader(self.piff, archive)
239 impl = PSF._read(reader, "piff", PiffLogger(_LOG))
240 return PiffWrapper(impl, bounds=self.bounds.deserialize(), stamp_size=self.stamp_size)
243class _ArchivePiffWriter:
244 """An adapter from the Piff serialization interface to the
245 `.serialization.OutputArchive` class.
247 Notes
248 -----
249 Piff has its own simple serialization framework (contributed upstream by
250 Rubin DM) that maps everything to dictionaries, structured numpy arrays,
251 and a library of GalSim WCS objects, with the native implementation writing
252 standalone FITS files. That mostly maps nicely to the `lsst.images`
253 archive system, but we don't get to leverage any Pydantic validation or
254 JSON schema functionality since we only get opaque dictionaries from Piff.
256 See `piff.FitsWriter` for most method documentation; this class is designed
257 to mimic it exactly (the Piff authors prefer to just use duck-typing rather
258 than ABCs or protocols for interface definition).
259 """
261 def __init__(self, base_name: str = ""):
262 self._base_name = base_name
263 self.structs: dict[str, PiffDict] = {}
264 self.tables: dict[str, tuple[np.ndarray, PiffDict]] = {}
265 self.wcs_models: dict[str, GalSimLocalWcsModel] = {}
266 self.writers: dict[str, _ArchivePiffWriter] = {}
268 def write_struct(self, name: str, struct: PiffDict) -> None:
269 self.structs[name] = {k: self._to_builtin(v) for k, v in struct.items()}
271 def write_table(self, name: str, array: np.ndarray, metadata: PiffDict | None = None) -> None:
272 self.tables[name] = (array, metadata or {})
274 def write_wcs_map(
275 self, name: str, wcs_map: dict[int, galsim.wcs.BaseWCS], pointing: galsim.CelestialCoord | None
276 ) -> None:
277 import galsim.wcs
279 match wcs_map:
280 case {0: galsim.wcs.PixelScale() as wcs} if pointing is None:
281 self.wcs_models[name] = GalSimPixelScaleModel(scale=wcs.scale)
282 case _:
283 raise NotImplementedError("PSFs with complex embedded WCSs are not supported.")
285 @contextmanager
286 def nested(self, name: str) -> Iterator[_ArchivePiffWriter]:
287 nested = _ArchivePiffWriter(self.get_full_name(name))
288 yield nested
289 self.writers[name] = nested
291 def get_full_name(self, name: str) -> str:
292 return f"{self._base_name}/{name}"
294 def serialize(self, archive: serialization.OutputArchive[Any]) -> PiffObjectModel:
295 """Serialize to an archive.
297 This method is intended to be used as the callable passed to
298 `.serialization.OutputArchive.serialize_direct` and
299 `.serialization.OutputArchive.serialize_pointer`, after first passing
300 this writer to a Piff object's ``write`` or ``_write`` method.
301 """
302 model = PiffObjectModel()
303 for name, struct in self.structs.items():
304 model.structs[name] = struct
305 for name, (array, metadata) in self.tables.items():
306 model.tables[name] = PiffTableModel(
307 metadata=metadata,
308 table=archive.add_structured_array(
309 array, name=name, update_header=lambda header: header.update(metadata)
310 ),
311 )
312 for name, wcs_model in self.wcs_models.items():
313 model.wcs[name] = wcs_model
314 for name, writer in self.writers.items():
315 model.objects[name] = archive.serialize_direct(name, writer.serialize)
316 return model
318 @staticmethod
319 def _to_builtin(val: Any) -> PiffScalar:
320 match val:
321 case np.integer():
322 return int(val)
323 case np.floating():
324 return float(val)
325 case np.str_():
326 return str(val)
327 return val
330class _ArchivePiffReader:
331 """An adapter from the Piff serialization interface to the
332 `.serialization.InputArchive` class.
334 See `ArchivePiffWriter` for additional notes.
335 """
337 def __init__(
338 self, object_model: PiffObjectModel, archive: serialization.InputArchive[Any], base_name: str = ""
339 ):
340 self._model = object_model
341 self._archive = archive
342 self._base_name = base_name
344 def read_struct(self, name: str) -> PiffDict | None:
345 return self._model.structs.get(name)
347 def read_table(self, name: str, metadata: PiffDict | None = None) -> np.ndarray | None:
348 table_model = self._model.tables.get(name)
349 if table_model is None:
350 return None
351 if metadata is not None:
352 metadata.update(table_model.metadata)
353 return self._archive.get_structured_array(
354 table_model.table, strip_header=astropy.io.fits.Header.clear
355 )
357 def read_wcs_map(
358 self, name: str, logger: piff.config.LoggerWrapper
359 ) -> tuple[dict[int, galsim.wcs.BaseWCS] | None, galsim.CelestialCoord | None]:
360 import galsim.wcs
362 match self._model.wcs.get(name):
363 case GalSimPixelScaleModel(scale=scale):
364 return {0: galsim.wcs.PixelScale(scale)}, None
365 case None:
366 return None, None
367 case unexpected:
368 raise serialization.ArchiveReadError(
369 f"{self.get_full_name(name)} should be a WCS or WCS map, not {unexpected!r}."
370 )
372 @contextmanager
373 def nested(self, name: str) -> Iterator[_ArchivePiffReader]:
374 nested_model = self._model.objects[name]
375 yield _ArchivePiffReader(nested_model, self._archive, self.get_full_name(name))
377 def get_full_name(self, name: str) -> str:
378 return f"{self._base_name}/{name}"