Convert data from view into copy (#153)

Author: snbianco

astrocut/ASDFCutout.py

@@ -226,6 +226,11 @@ def _get_cutout_data(self, data: np.ndarray, wcs: WCS, pixel_coords: Tuple[int,
 
         log.debug('Image cutout shape: %s', img_cutout.shape)
 
+        # Data in the Cutout2D object is a view into the original data. We need to deep copy the 
+        # data in the cutout object to ensure that it is fully independent of the original data 
+        # and that it does not take up the same amount of storage.
+        img_cutout.data = np.array(img_cutout.data, copy=True)
+
         return img_cutout
 
     def _slice_gwcs(self, cutout: Cutout2D, gwcs: gwcs.wcs.WCS) -> gwcs.wcs.WCS:

astrocut/tests/test_ASDFCutout.py

@@ -159,6 +159,7 @@ def test_asdf_cutout_write_to_file(test_images, center_coord, cutout_size, tmpdi
             assert 'meta' in af.tree['roman']
             assert np.all(af.tree['roman']['data'] == cutout.cutouts[i].data)
             assert af.tree['roman']['meta']['wcs'].pixel_shape == (10, 10)
+            assert Path(asdf_file).stat().st_size < Path(test_images[i]).stat().st_size
 
     # Write cutouts to FITS files on disk
     cutout = ASDFCutout(test_images, center_coord, cutout_size)
@@ -169,6 +170,7 @@ def test_asdf_cutout_write_to_file(test_images, center_coord, cutout_size, tmpdi
             assert np.all(hdul[0].data == cutout.cutouts[i].data)
             assert hdul[0].header['NAXIS1'] == 10
             assert hdul[0].header['NAXIS2'] == 10
+            assert Path(fits_file).stat().st_size < Path(test_images[i]).stat().st_size
 
 
 def test_asdf_cutout_partial(test_images, center_coord, cutout_size):