Add converter and schema for basic astropy.wcs.WCS objects

asdf_astropy/converters/__init__.py

@@ -15,6 +15,7 @@
     "FitsConverter",
     "AsdfFitsConverter",
     "AstropyFitsConverter",
+    "FitsWCSConverter",
     "ColumnConverter",
     "AstropyTableConverter",
     "AsdfTableConverter",
@@ -51,7 +52,7 @@
     SkyCoordConverter,
     SpectralCoordConverter,
 )
-from .fits import AsdfFitsConverter, AstropyFitsConverter, FitsConverter
+from .fits import AsdfFitsConverter, AstropyFitsConverter, FitsConverter, FitsWCSConverter
 from .table import AsdfTableConverter, AstropyTableConverter, ColumnConverter, NdarrayMixinConverter
 from .time import TimeConverter, TimeDeltaConverter
 from .transform import (

asdf_astropy/converters/fits/__init__.py

@@ -2,6 +2,8 @@
     "FitsConverter",
     "AsdfFitsConverter",
     "AstropyFitsConverter",
+    "FitsWCSConverter",
 ]
 
 from .fits import AsdfFitsConverter, AstropyFitsConverter, FitsConverter
+from .fitswcs import FitsWCSConverter

asdf_astropy/converters/fits/fitswcs.py

@@ -0,0 +1,29 @@
+from asdf.extension import Converter
+
+
+class FitsWCSConverter(Converter):
+    """
+    Converter for serializing and deserializing `astropy.wcs.WCS` objects.
+
+    This converter currently supports the serialization of simple WCS objects
+    by preserving the `wcs.to_header()` data. It does not support complex WCS objects
+    such as tabular or distortion WCSes.
+
+    Future work:
+        - Until the support for tabular and distortion WCSes is added, throw error for such WCSes when passed through in the converter
+        - Implement mechanisms to detect tabular and distortion WCSes and support their serialization
+    """
+    tags = ("tag:astropy.org:astropy/fits/fitswcs-*",)
+    types = ("astropy.wcs.wcs.WCS", )
+
+    def from_yaml_tree(self, node, tag, ctx):
+        from astropy.wcs import WCS
+
+        header = node["header"]
+        wcs = WCS(header)
+        return wcs
+
+    def to_yaml_tree(self, wcs, tag, ctx):
+        node = {}
+        node["header"] = dict(wcs.to_header())
+        return node

asdf_astropy/converters/fits/tests/test_fitswcs.py

@@ -0,0 +1,41 @@
+import asdf
+import pytest
+from astropy.wcs import WCS
+
+
+def create_wcs():
+    header = {
+    'CTYPE1': 'TIME',
+    'CUNIT1': 'min',
+    'CDELT1': 0.4,
+    'CRPIX1': 0,
+    'CRVAL1': 0,
+    'CTYPE2': 'WAVE',
+    'CUNIT2': 'Angstrom',
+    'CDELT2': 0.2,
+    'CRPIX2': 0,
+    'CRVAL2': 0,
+    'CTYPE3': 'HPLT-TAN',
+    'CUNIT3': 'arcsec',
+    'CDELT3': 20,
+    'CRPIX3': 0,
+    'CRVAL3': 0,
+    'CTYPE4': 'HPLN-TAN',
+    'CUNIT4': 'arcsec',
+    'CDELT4': 5,
+    'CRPIX4': 5,
+    'CRVAL4': 0,
+    }
+    return WCS(header)
+
+@pytest.mark.parametrize("wcs", [create_wcs()])
+def test_wcs_serialization(wcs, tmp_path):
+    file_path = tmp_path / "test_wcs.asdf"
+    with asdf.AsdfFile() as af:
+        af["wcs"] = wcs
+        af.write_to(file_path)
+
+    with asdf.open(file_path) as af:
+        loaded_wcs = af["wcs"]
+
+    assert wcs.to_header() == loaded_wcs.to_header()

asdf_astropy/extensions.py

@@ -13,6 +13,7 @@
 from .converters.coordinates.sky_coord import SkyCoordConverter
 from .converters.coordinates.spectral_coord import SpectralCoordConverter
 from .converters.fits.fits import AsdfFitsConverter, AstropyFitsConverter
+from .converters.fits.fitswcs import FitsWCSConverter
 from .converters.table.table import AsdfTableConverter, AstropyTableConverter, ColumnConverter, NdarrayMixinConverter
 from .converters.time.time import TimeConverter
 from .converters.time.time_delta import TimeDeltaConverter
@@ -482,6 +483,7 @@
     AstropyTableConverter(),
     AstropyFitsConverter(),
     NdarrayMixinConverter(),
+    FitsWCSConverter(),
 ]
 
 _COORDINATES_MANIFEST_URIS = [

asdf_astropy/resources/manifests/astropy-1.0.0.yaml

@@ -28,6 +28,11 @@ tags:
     be accessible in its proper form in the ASDF file.
 
     Only image and binary table extensions are supported.
+- tag_uri: tag:astropy.org:astropy/fits/fitswcs-1.0.0
+  schema_uri: http://astropy.org/schemas/astropy/fits/fitswcs-1.0.0
+  title: Represents an astropy.wcs.WCS object
+  description: |-
+    Supports serialization of the simple wcs objects header
 - tag_uri: tag:astropy.org:astropy/table/table-1.0.0
   schema_uri: http://astropy.org/schemas/astropy/table/table-1.0.0
   title: A table.

asdf_astropy/resources/schemas/fits/fitswcs-1.0.0.yaml

@@ -0,0 +1,17 @@
+%YAML 1.1
+---
+$schema: "http://stsci.edu/schemas/yaml-schema/draft-01"
+id: "http://astropy.org/schemas/astropy/fits/fitswcs-1.0.0"
+
+title:
+  Represents the fits object
+
+description:
+  Represents the fits object
+
+allOf:
+  - tag: "tag:astropy.org:astropy/fits/fitswcs-1.0.0"
+  - type: object
+    properties:
+      header:
+        type: object