Make compute_scale robust to case where fiducial coordinates are ousi…

…de of bounding box

jdaviz/configs/imviz/wcs_utils.py

@@ -6,6 +6,7 @@
 import base64
 import math
 from io import BytesIO
+import warnings
 
 import matplotlib.pyplot as plt
 import numpy as np
@@ -575,7 +576,13 @@ def compute_scale(wcs, fiducial, disp_axis, pscale_ratio=1):
     if spectral and disp_axis is None:  # pragma: no cover
         raise ValueError('If input WCS is spectral, a disp_axis must be given')
 
-    crpix = np.array(wcs.invert(*fiducial))
+    if wcs.in_image(*fiducial):
+        crpix = np.array(wcs.invert(*fiducial))
+    else:
+        # At this point we know the bounding box is probably defined, so we can
+        # use the central coordinate inside the bounding box
+        warnings.warn("WCS fiducial coordinates not inside bounding box")
+        crpix = np.mean(wcs.pixel_bounds, axis=1)
 
     delta = np.zeros_like(crpix)
     spatial_idx = np.where(np.array(wcs.output_frame.axes_type) == 'SPATIAL')[0]