hips2fits: make Pillow an optional dependency with a clear ImportError

CHANGES.rst

@@ -103,6 +103,13 @@ svo_fps
 - Add ``get_filter_metadata`` to allow retrieval of filter metadata. [#3528]
 - Add ``get_zeropoint`` to allow retrieval of filter zeropoints and allow kwarg passing to ``get_filter_metadata``. [#3545]
 
+hips2fits
+^^^^^^^^^
+
+- ``Pillow`` is now an optional dependency: importing ``astroquery.hips2fits`` no
+  longer crashes when Pillow is not installed. A clear ``ImportError`` is raised
+  only when a jpg/png response is actually decoded. [#3619]
+
 heasarc
 ^^^^^^^
 - Add ``query_constraints`` to allow querying of different catalog columns. [#3403]

astroquery/hips2fits/core.py

@@ -9,8 +9,6 @@
 from astropy.io import fits
 from astropy.coordinates import Angle
 import astropy.units as u
-from PIL import Image
-
 from astropy.utils.exceptions import AstropyUserWarning
 
 from ..query import BaseQuery
@@ -325,6 +323,13 @@ def _parse_result(self, response, verbose, format):
                 return hdul
             else:
                 # jpg/png formats
+                try:
+                    from PIL import Image
+                except ImportError:
+                    raise ImportError(
+                        "Pillow is required to decode jpg/png responses from hips2fits. "
+                        "Install it with: pip install Pillow"
+                    )
                 bytes = io.BytesIO(bytes_str)
                 im = Image.open(bytes)
                 data = np.asarray(im)

astroquery/hips2fits/tests/test_hips2fits.py

@@ -1,4 +1,8 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
+import sys
+from unittest.mock import MagicMock, patch
+
+import pytest
 from astropy import wcs as astropy_wcs
 from matplotlib.colors import Colormap
 from astropy.coordinates import Angle, Longitude, Latitude
@@ -7,6 +11,27 @@
 from ..core import hips2fits
 
 
+class TestHips2fits:
+
+    def test_jpg_format_requires_pillow(self):
+        mock_response = MagicMock()
+        mock_response.status_code = 200
+        mock_response.content = b'fake_image_bytes'
+
+        with patch.dict(sys.modules, {'PIL': None, 'PIL.Image': None}):
+            with pytest.raises(ImportError, match="Pillow is required"):
+                hips2fits._parse_result(mock_response, verbose=False, format='jpg')
+
+    def test_png_format_requires_pillow(self):
+        mock_response = MagicMock()
+        mock_response.status_code = 200
+        mock_response.content = b'fake_image_bytes'
+
+        with patch.dict(sys.modules, {'PIL': None, 'PIL.Image': None}):
+            with pytest.raises(ImportError, match="Pillow is required"):
+                hips2fits._parse_result(mock_response, verbose=False, format='png')
+
+
 class TestHips2fitsRemote:
 
     # Create a new WCS astropy object

pyproject.toml

@@ -61,6 +61,7 @@ all = [
    "boto3",
    "botocore",
    "regions>=0.5",
+   "Pillow",
 ]
 
 [build-system]