Fix a bug in resampled_wcs_from_models (spacetelescope#9186)

changes/9186.resample.rst

@@ -0,0 +1 @@
+Fix a bug in ``resampled_wcs_from_models``.

jwst/resample/resample_spec.py

@@ -16,7 +16,7 @@
 
 from stdatamodels.jwst import datamodels
 
-from jwst.assign_wcs.util import compute_scale, wrap_ra
+from jwst.assign_wcs.util import compute_scale, wcs_bbox_from_shape, wrap_ra
 from jwst.resample import resample_utils
 from jwst.resample.resample import ResampleImage
 from jwst.datamodels import ModelLibrary
@@ -512,8 +512,7 @@ def build_nirspec_output_wcs(self, input_models, refmodel=None,
 
         # Compute bounding box and output array shape.
         data_size = (ny, n_lam)
-        bounding_box = resample_utils.wcs_bbox_from_shape(data_size)
-        output_wcs.bounding_box = bounding_box
+        output_wcs.bounding_box = wcs_bbox_from_shape(data_size)
         output_wcs.array_shape = data_size
 
         return output_wcs
@@ -795,7 +794,7 @@ def build_interpolated_output_wcs(self, input_models, pixel_scale_ratio=1.0):
         # turn the size into a numpy shape in (y, x) order
         output_wcs.array_shape = output_array_size[::-1]
         output_wcs.pixel_shape = output_array_size
-        bounding_box = resample_utils.wcs_bbox_from_shape(output_array_size[::-1])
+        bounding_box = wcs_bbox_from_shape(output_array_size[::-1])
         output_wcs.bounding_box = bounding_box
 
         return output_wcs
@@ -904,7 +903,7 @@ def build_nirspec_lamp_output_wcs(self, input_models, pixel_scale_ratio):
         # turn the size into a numpy shape in (y, x) order
         output_wcs.array_shape = output_array_size[::-1]
         output_wcs.pixel_shape = output_array_size
-        bounding_box = resample_utils.wcs_bbox_from_shape(output_array_size[::-1])
+        bounding_box = wcs_bbox_from_shape(output_array_size[::-1])
         output_wcs.bounding_box = bounding_box
 
         return output_wcs

jwst/resample/resample_utils.py

@@ -12,7 +12,6 @@
 
 from stcal.alignment.util import (
     compute_scale,
-    wcs_bbox_from_shape,
     wcs_from_sregions,
 )
 from stcal.resample import UnsupportedWCSError
@@ -36,7 +35,6 @@
 
 def resampled_wcs_from_models(
         input_models,
-        ref_wcs=None,
         pixel_scale_ratio=1.0,
         pixel_scale=None,
         output_shape=None,
@@ -54,10 +52,6 @@ def resampled_wcs_from_models(
     input_models : `~jwst.datamodel.ModelLibrary`
         Each datamodel must have a ``model.meta.wcs`` set to a ~gwcs.WCS object.
 
-    ref_wcs : WCS object
-        A WCS used as reference for the creation of the output
-        coordinate frame, projection, and scaling and rotation transforms.
-
     pixel_scale_ratio : float, optional
         Desired pixel scale ratio defined as the ratio of the desired output
         pixel scale to the first input model's pixel scale computed from this
@@ -111,22 +105,16 @@ def resampled_wcs_from_models(
     # build a list of WCS of all input models:
     sregion_list = []
     ref_wcs = None
-    ref_wcsinfo = None
-    shape = None
 
     with input_models:
         for model in input_models:
-            w = model.meta.wcs
-            if ref_wcsinfo is None:
+            if ref_wcs is None:
                 ref_wcsinfo = model.meta.wcsinfo.instance
+                ref_wcs = deepcopy(model.meta.wcs)
                 shape = model.data.shape
-            if ref_wcs is None:
-                ref_wcs = w
-            # make sure all WCS objects have the bounding_box defined:
-            if w.bounding_box is None:
-                w.bounding_box = wcs_bbox_from_shape(shape)
+
             sregion_list.append(model.meta.wcsinfo.s_region)
-            input_models.shelve(model)
+            input_models.shelve(model, modify=False)
 
     if not sregion_list:
         raise ValueError("No input models.")
@@ -173,6 +161,7 @@ def resampled_wcs_from_models(
         crpix=crpix,
         crval=crval
     )
+
     return wcs, pscale_in0, pixel_scale, pixel_scale_ratio