Merge pull request #358 from STBadman/main

Allow user to specify the center of map coordinates in `pfsspy.utils.carr_cea_wcs_header`

pfsspy/tests/test_utils.py

@@ -1,3 +1,5 @@
+import datetime
+
 import astropy.units as u
 import numpy as np
 import pytest
@@ -115,3 +117,36 @@ def test_roll_map(gong_map):
     with pytest.raises(ValueError,
                        match='lh_edge_lon must be in'):
         utils.roll_map(adapt_map, lh_edge_lon=361 * u.deg)
+
+
+def test_cea_header():
+    # Assert default reference pixel is at 0 deg lon
+    cea_default = utils.carr_cea_wcs_header(
+        datetime.datetime(2020, 1, 1),
+        [360, 180]
+    )
+    assert cea_default['crval1'] == 0.0
+
+    # Assert custom reference pixel is expected lon
+    cea_shift = utils.carr_cea_wcs_header(
+        datetime.datetime(2020, 1, 1),
+        [360, 180],
+        map_center_longitude=10.0*u.deg
+    )
+    assert cea_shift['crval1'] == 10.0
+
+    # Test reference pixel shift error handling
+    # 1: No units
+    with pytest.raises(u.UnitTypeError):
+        cea_default = utils.carr_cea_wcs_header(
+            datetime.datetime(2020, 1, 1),
+            [360, 180],
+            map_center_longitude=0.0
+        )
+    # 2: Wrong Units
+    with pytest.raises(u.UnitTypeError):
+        cea_default = utils.carr_cea_wcs_header(
+            datetime.datetime(2020, 1, 1),
+            [360, 180],
+            map_center_longitude=0.0*u.m
+        )

pfsspy/utils.py

@@ -88,7 +88,8 @@ def load_adapt(adapt_path):
     return adaptMapSequence
 
 
-def carr_cea_wcs_header(dtime, shape):
+@u.quantity_input
+def carr_cea_wcs_header(dtime, shape, *, map_center_longitude=0*u.deg):
     """
     Create a Carrington WCS header for a Cylindrical Equal Area (CEA)
     projection. See [1]_ for information on how this is constructed.
@@ -100,6 +101,10 @@ def carr_cea_wcs_header(dtime, shape):
     shape : tuple
         Map shape. The first entry should be number of points in longitude, the
         second in latitude.
+    map_center_longitude : astropy.units.Quantity
+        Change the world coordinate longitude of the central image pixel to allow
+        for different roll angles of the Carrington map. Default to 0 deg. Must
+        be supplied with units of `astropy.units.deg`
 
     References
     ----------
@@ -111,7 +116,7 @@ def carr_cea_wcs_header(dtime, shape):
     obstime = dtime or astropy.time.Time('2000-1-1')
 
     frame_out = coord.SkyCoord(
-        0 * u.deg, 0 * u.deg, const.R_sun, obstime=obstime,
+        map_center_longitude, 0 * u.deg, const.R_sun, obstime=obstime,
         frame="heliographic_carrington", observer='self')
     # Construct header
     header = sunpy.map.make_fitswcs_header(