feat: add support of Regions in from_astropy_regions

Author: ManonMarchand

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+* Add support of `regions.Regions` [#163]
 * Creation of a MOC from a zone (defined by min/max ra and dec)`MOC.from_zone`
 * Creation of a single MOC from a lot of small cones is faster with the new option in
 `MOC.from_cones`: the keyword 'union_strategy' can now take the value 'small_cones'.

python/mocpy/moc/moc.py

@@ -1844,7 +1844,7 @@ def from_astropy_regions(cls, region, max_depth: int):
             The supported sky regions are `~regions.CircleSkyRegion`,
             `~regions.CircleAnnulusSkyRegion`, `~regions.EllipseSkyRegion`,
             `~regions.RectangleSkyRegion`, `~regions.PolygonSkyRegion`,
-            `~regions.PointSkyRegion`.
+            `~regions.PointSkyRegion`, `~regions.Regions`.
         max_depth : int
             The maximum HEALPix cell resolution of the MOC. Should be comprised between
             0 and 29.
@@ -1853,6 +1853,14 @@ def from_astropy_regions(cls, region, max_depth: int):
         -------
         `~mocpy.moc.MOC`
 
+        Notes
+        -----
+        - For the `~regions.Regions`, the returned MOC will be the union of all the regions.
+        - For the `~regions.PolygonSkyRegion` and the `~regions.RectangleSkyRegion`, the MOC
+        will consider the sides to follow great circles on the sky sphere while in
+        astropy-regions the sides follow straight lines in the projected space (depending on
+        a given WCS, see issue https://github.com/astropy/regions/issues/564).
+
         Examples
         --------
         >>> from astropy.coordinates import SkyCoord
@@ -1869,6 +1877,7 @@ def from_astropy_regions(cls, region, max_depth: int):
             regions.RectangleSkyRegion,
             regions.PolygonSkyRegion,
             regions.PointSkyRegion,
+            regions.Regions,
         )
         if isinstance(region, regions.CircleSkyRegion):
             center = region.center.icrs
@@ -1927,6 +1936,13 @@ def from_astropy_regions(cls, region, max_depth: int):
             return cls.from_polygon_skycoord(region.vertices, max_depth=max_depth)
         if isinstance(region, regions.PointSkyRegion):
             return cls.from_skycoords(region.center, max_norder=max_depth)
+        if isinstance(region, regions.Regions):
+            mocs = [
+                cls.from_astropy_regions(reg, max_depth=max_depth) for reg in region
+            ]
+            if len(mocs) == 1:
+                return mocs[0]
+            return mocs[0].union(*mocs[1:])  # fastest multi-union
 
         raise ValueError(
             "'from_astropy_regions' does not support this region type."

python/mocpy/tests/test_moc.py

@@ -689,14 +689,18 @@ def test_from_astropy_regions():
     # polygons
     vertices = SkyCoord([1, 2, 2], [1, 1, 2], unit="deg", frame="fk5")
     polygon = regions.PolygonSkyRegion(vertices)
-    moc = MOC.from_astropy_regions(polygon, max_depth=10)
-    assert all(moc.contains_skycoords(vertices))
+    moc_polygon = MOC.from_astropy_regions(polygon, max_depth=10)
+    assert all(moc_polygon.contains_skycoords(vertices))
     # points
     point = SkyCoord("+23h20m48.3s +61d12m06s")
     region_point = regions.PointSkyRegion(point)
-    moc = MOC.from_astropy_regions(region_point, max_depth=10)
-    assert moc.max_order == 10
-    assert moc.contains_skycoords(point)
+    moc_point = MOC.from_astropy_regions(region_point, max_depth=10)
+    assert moc_point.max_order == 10
+    assert moc_point.contains_skycoords(point)
+    # multi regions
+    multi_region = regions.Regions([region_point, polygon])
+    moc = MOC.from_astropy_regions(multi_region, max_depth=10)
+    assert moc == moc_polygon + moc_point
 
 
 # TODO: IMPROVE THE ALGO