Expand test and fix implementation of pixel2world_single_axis

glue/core/coordinate_helpers.py

@@ -53,9 +53,19 @@ def pixel2world_single_axis(wcs, *pixel, world_axis=None):
             pixel_new.append(p.flat[0])
     pixel = np.broadcast_arrays(*pixel_new)
 
-    result = wcs.pixel_to_world_values(*pixel)
+    # In the case of 1D WCS, there is an astropy issue which prevents us from
+    # passing arbitrary shapes - see https://github.com/astropy/astropy/issues/12154
+    # Therefore, we ravel the values and reshape afterwards
+
+    if len(pixel) == 1 and pixel[0].ndim > 1:
+        pixel_shape = pixel[0].shape
+        pixel = [pixel[0].ravel()]
+        result = wcs.pixel_to_world_values(*pixel)
+        result = result.reshape(pixel_shape)
+    else:
+        result = wcs.pixel_to_world_values(*pixel)
 
-    if len(pixel) > 1 or np.ndim(result) > 1:
+    if len(pixel) > 1:
         result = result[world_axis]
 
     return np.broadcast_to(result, original_shape)

glue/core/tests/test_coordinates.py

@@ -363,6 +363,24 @@ def test_pixel2world_single_axis():
     assert_allclose(pixel2world_single_axis(coord, x, y, z, world_axis=2), [1.5, 1.5, 1.5])
 
 
+def test_pixel2world_single_axis_1d():
+
+    # Regression test for issues that occurred for 1D WCSes
+
+    coord = WCSCoordinates(naxis=1)
+    coord.wcs.ctype = ['FREQ']
+    coord.wcs.crpix = [1]
+    coord.wcs.crval = [1]
+    coord.wcs.cdelt = [1]
+
+    x = np.array([0.2, 0.4, 0.6])
+    expected = np.array([1.2, 1.4, 1.6])
+
+    assert_allclose(pixel2world_single_axis(coord, x, world_axis=0), expected)
+    assert_allclose(pixel2world_single_axis(coord, x.reshape((1, 3)), world_axis=0), expected.reshape((1, 3)))
+    assert_allclose(pixel2world_single_axis(coord, x.reshape((3, 1)), world_axis=0), expected.reshape((3, 1)))
+
+
 def test_affine():
 
     matrix = np.array([[2, 3, -1], [1, 2, 2], [0, 0, 1]])