allow DN as a unit on Map

sunpy · Apr 23, 2024 · 266115c · 266115c
1 parent 9529ee0
commit 266115c
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Showing 3 changed files with 32 additions and 29 deletions.
diff --git a/sunpy/map/mapbase.py b/sunpy/map/mapbase.py
@@ -537,7 +537,7 @@ def _new_instance_from_op(self, new_data):
         operations.
         """
         new_meta = copy.deepcopy(self.meta)
-        new_meta['bunit'] = new_data.unit.to_string('fits')
+        new_meta['bunit'] = new_data.unit.to_string()
         return self._new_instance(new_data.value, new_meta, plot_settings=self.plot_settings)
 
     def __neg__(self):
@@ -727,19 +727,22 @@ def max(self, *args, **kwargs):
     @staticmethod
     def _parse_fits_unit(unit_str):
         replacements = {'gauss': 'G',
-                        'dn': 'ct',
-                        'dn/s': 'ct/s',
                         'counts / pixel': 'ct/pix',}
         if unit_str.lower() in replacements:
             unit_str = replacements[unit_str.lower()]
         unit = u.Unit(unit_str, format='fits', parse_strict='silent')
         if isinstance(unit, u.UnrecognizedUnit):
-            warn_metadata(f'Could not parse unit string "{unit_str}" as a valid FITS unit.\n'
-                          f'See {_META_FIX_URL} for how to fix metadata before loading it '
-                          'with sunpy.map.Map.\n'
-                          'See https://fits.gsfc.nasa.gov/fits_standard.html for '
-                          'the FITS unit standards.')
-            unit = None
+            # NOTE: Special case DN here as it is not part of the FITS standard, but
+            # is widely used and is also a recognized astropy unit
+            if 'DN' in str(unit):
+                unit = u.Unit(unit_str)
+            else:
+                warn_metadata(f'Could not parse unit string "{unit_str}" as a valid FITS unit.\n'
+                              f'See {_META_FIX_URL} for how to fix metadata before loading it '
+                               'with sunpy.map.Map.\n'
+                               'See https://fits.gsfc.nasa.gov/fits_standard.html for '
+                               'the FITS unit standards.')
+                unit = None
         return unit
 
     @property

diff --git a/sunpy/map/tests/conftest.py b/sunpy/map/tests/conftest.py
@@ -96,7 +96,7 @@ def generic_map():
         'detector': 'bar',
         'wavelnth': 10,
         'waveunit': 'm',
-        'bunit': 'ct/s',
+        'bunit': 'DN/s',
     }
     return sunpy.map.Map((data, header))
 

diff --git a/sunpy/map/tests/test_mapbase.py b/sunpy/map/tests/test_mapbase.py
@@ -223,7 +223,7 @@ def test_std(generic_map):
 
 
 def test_unit(generic_map):
-    assert generic_map.unit == u.ct / u.s
+    assert generic_map.unit == u.DN / u.s
     generic_map.meta['bunit'] = 'not a unit'
     with pytest.warns(SunpyMetadataWarning, match='Could not parse unit string "not a unit"'):
         assert generic_map.unit is None
@@ -1682,12 +1682,10 @@ def check_arithmetic_value_and_units(map_new, data_expected):
 
 
 @pytest.mark.parametrize('value', [
-    10 * u.ct,
-    10 * u.mct,
-    u.Quantity([10], u.ct),
-    u.Quantity(np.random.rand(128), u.ct),
-    u.Quantity(np.random.rand(128, 128), u.ct),
-    u.Quantity(np.random.rand(128, 128), u.mct),
+    10 * u.DN,
+    u.Quantity([10], u.DN),
+    u.Quantity(np.random.rand(128), u.DN),
+    u.Quantity(np.random.rand(128, 128), u.DN),
 ])
 def test_map_arithmetic_addition_subtraction(aia171_test_map, value):
     new_map = aia171_test_map + value
@@ -1701,10 +1699,10 @@ def test_map_arithmetic_addition_subtraction(aia171_test_map, value):
 
 
 @pytest.mark.parametrize('value', [
-    10 * u.ct,
-    u.Quantity([10], u.ct),
-    u.Quantity(np.random.rand(128), u.ct),
-    u.Quantity(np.random.rand(128, 128), u.ct),
+    10 * u.s,
+    u.Quantity([10], u.s),
+    u.Quantity(np.random.rand(128), u.s),
+    u.Quantity(np.random.rand(128, 128), u.s),
     10.0,
     np.random.rand(128),
     np.random.rand(128, 128),
@@ -1741,14 +1739,16 @@ def test_map_arithmetic_operations_raise_exceptions(aia171_test_map, value):
     with pytest.raises(TypeError):
         _ = value / aia171_test_map
 
-
-def test_parse_fits_units():
-    # Check that we parse a BUNIT of G correctly.
-    out_unit = GenericMap._parse_fits_unit("Gauss")
-    assert out_unit == u.G
-
-    out_unit = GenericMap._parse_fits_unit("G")
-    assert out_unit == u.G
+@pytest.mark.parametrize(('units_string','expected_unit'),[
+    ('Gauss', u.G),
+    ('G', u.G),
+    ('DN', u.DN),
+    ('DN/s', u.DN/u.s),
+    ('counts / pixel', u.ct/u.pix),
+])
+def test_parse_fits_units(units_string, expected_unit):
+    out_unit = GenericMap._parse_fits_unit(units_string)
+    assert out_unit == expected_unit
 
 
 def test_only_cd():