Add support for compound bounding boxes and ignored bounding box entr…

…ies in `grid_from_bounding_box` (#519)

CHANGES.rst

@@ -9,6 +9,8 @@
 
 - Synchronize ``region.py`` with the copies of it in JWST and Romancal. [#517]
 
+- Add support for compound bounding boxes and ignored bounding box entries. [#519]
+
 0.21.0 (2024-03-10)
 -------------------
 

gwcs/tests/test_wcs.py

@@ -7,7 +7,8 @@
 import numpy as np
 from numpy.testing import assert_allclose, assert_equal
 
-from astropy.modeling import models
+from astropy.modeling import models, bind_compound_bounding_box
+from astropy.modeling.bounding_box import ModelBoundingBox
 from astropy import coordinates as coord
 from astropy.io import fits
 from astropy import units as u
@@ -391,6 +392,61 @@ def test_grid_from_bounding_box_step():
     with pytest.raises(ValueError):
         grid_from_bounding_box(bb, step=(1, 2, 1))
 
+def test_grid_from_model_bounding_box():
+    bbox = ((-1, 1), (0, 1))
+    # Truth grid
+    grid_truth = grid_from_bounding_box(bbox)
+
+    # Create a bounding box
+    model = models.Const2D() & models.Const1D()
+    model.inputs = ("x", "y", "slit_name")
+    model.bounding_box = ModelBoundingBox(
+        {
+            "x": bbox[0],
+            "y": bbox[1],
+        },
+        model=model,
+        ignored=["slit_name"],
+        order="F",
+    )
+    grid = grid_from_bounding_box(model.bounding_box)
+
+    assert np.all(grid == grid_truth)
+
+
+def test_grid_from_compound_bounding_box():
+    bbox = ((-1, 1), (0, 1))
+    # Truth grid
+    grid_truth = grid_from_bounding_box(bbox)
+
+    # Create a compound bounding box
+    model = models.Const2D() & models.Const1D()
+    model.inputs = ("x", "y", "slit_name")
+    bind_compound_bounding_box(
+        model,
+        {
+            (200,) : {
+                "x": bbox[0],
+                "y": bbox[1],
+            },
+            (300,) :{
+                "x": (-2, 2),
+                "y": (0, 2),
+            }
+        },
+        [("slit_name",)],
+        order="F",
+    )
+    grid = grid_from_bounding_box(model.bounding_box, selector=(200,))
+
+    assert np.all(grid == grid_truth)
+
+    # Capture errors
+    with pytest.raises(ValueError, match=r"Cannot use selector with a non-CompoundBoundingBox"):
+        grid_from_bounding_box(model.bounding_box[(300,)], selector=(300,))
+    with pytest.raises(ValueError, match=r"selector must be set when bounding_box is a CompoundBoundingBox"):
+        grid_from_bounding_box(model.bounding_box)
+
 
 def test_wcs_from_points():
     np.random.seed(0)

gwcs/wcstools.py

@@ -5,6 +5,7 @@
 from astropy.modeling.core import Model
 from astropy.modeling import projections
 from astropy.modeling import models, fitting
+from astropy.modeling.bounding_box import CompoundBoundingBox, ModelBoundingBox
 from astropy import coordinates as coord
 from astropy import units as u
 
@@ -139,7 +140,7 @@ def _frame2D_transform(fiducial, **kwargs):
                    }
 
 
-def grid_from_bounding_box(bounding_box, step=1, center=True):
+def grid_from_bounding_box(bounding_box, step=1, center=True, selector=None):
     """
     Create a grid of input points from the WCS bounding_box.
 
@@ -151,11 +152,14 @@ def grid_from_bounding_box(bounding_box, step=1, center=True):
 
     Parameters
     ----------
-    bounding_box : tuple
+    bounding_box : tuple | ~astropy.modeling.bounding_box.ModelBoundingBox | ~astropy.modeling.bounding_box.CompoundBoundingBox
         The bounding_box of a WCS object, `~gwcs.wcs.WCS.bounding_box`.
     step : scalar or tuple
         Step size for grid in each dimension.  Scalar applies to all dimensions.
     center : bool
+    selector : tuple | None
+        If selector is set then it must be a selector tuple and bounding_box must
+        be a CompoundBoundingBox.
 
     The bounding_box is in order of X, Y [, Z] and the output will be in the
     same order.
@@ -187,6 +191,26 @@ def grid_from_bounding_box(bounding_box, step=1, center=True):
     """
     def _bbox_to_pixel(bbox):
         return (np.floor(bbox[0] + 0.5), np.ceil(bbox[1] - 0.5))
+
+    if selector is not None and not isinstance(bounding_box, CompoundBoundingBox):
+        raise ValueError("Cannot use selector with a non-CompoundBoundingBox")
+
+    if isinstance(bounding_box, CompoundBoundingBox):
+        if selector is None:
+            raise ValueError("selector must be set when bounding_box is a CompoundBoundingBox")
+
+        bounding_box = bounding_box[selector]
+
+    if isinstance(bounding_box, ModelBoundingBox):
+        input_names = bounding_box.model.inputs
+
+        # Get tuple of tuples of the bounding box values
+        bounding_box = tuple(
+            tuple(bounding_box[name])
+            for name in input_names
+            if name not in bounding_box.ignored_inputs
+        )
+
     # 1D case
     if np.isscalar(bounding_box[0]):
         nd = 1