Merge pull request #277 from larrybradley/bbox

Add BoundingBox union and intersection

CHANGES.rst

@@ -1,7 +1,12 @@
 0.4 (Unreleased)
 ================
 
-- No changes yet.
+New Features
+------------
+
+- Added ``union`` and ``intersection`` methods to the ``BoundingBox``
+  class. [#277]
+
 
 0.3 (2018-09-09)
 ================

regions/core/bounding_box.py

@@ -132,6 +132,12 @@ def __eq__(self, other):
             (self.iymax == other.iymax)
         )
 
+    def __or__(self, other):
+        return self.union(other)
+
+    def __and__(self, other):
+        return self.intersection(other)
+
     def __repr__(self):
         data = self.__dict__
         data['name'] = self.__class__.__name__
@@ -255,3 +261,61 @@ def plot(self, origin=(0, 0), ax=None, **kwargs):
 
         reg = self.to_region()
         return reg.plot(origin=origin, ax=ax, **kwargs)
+
+    def union(self, other):
+        """
+        Return a `BoundingBox` representing the union of this
+        `BoundingBox` with another `BoundingBox`.
+
+        Parameters
+        ----------
+        other : `~photutils.BoundingBox`
+            The `BoundingBox` to join with this one.
+
+        Returns
+        -------
+        result : `~photutils.BoundingBox`
+            A `BoundingBox` representing the union of the input
+            `BoundingBox` with this one.
+        """
+
+        if not isinstance(other, BoundingBox):
+            raise TypeError('BoundingBox can be joined only with another '
+                            'BoundingBox.')
+
+        ixmin = min((self.ixmin, other.ixmin))
+        ixmax = max((self.ixmax, other.ixmax))
+        iymin = min((self.iymin, other.iymin))
+        iymax = max((self.iymax, other.iymax))
+
+        return BoundingBox(ixmin=ixmin, ixmax=ixmax, iymin=iymin, iymax=iymax)
+
+    def intersection(self, other):
+        """
+        Return a `BoundingBox` representing the intersection of this
+        `BoundingBox` with another `BoundingBox`.
+
+        Parameters
+        ----------
+        other : `~photutils.BoundingBox`
+            The `BoundingBox` to intersect with this one.
+
+        Returns
+        -------
+        result : `~photutils.BoundingBox`
+            A `BoundingBox` representing the intersection of the input
+            `BoundingBox` with this one.
+        """
+
+        if not isinstance(other, BoundingBox):
+            raise TypeError('BoundingBox can be intersected only with '
+                            'another BoundingBox.')
+
+        ixmin = max(self.ixmin, other.ixmin)
+        ixmax = min(self.ixmax, other.ixmax)
+        iymin = max(self.iymin, other.iymin)
+        iymax = min(self.iymax, other.iymax)
+        if ixmax < ixmin or iymax < iymin:
+            return None
+
+        return BoundingBox(ixmin=ixmin, ixmax=ixmax, iymin=iymin, iymax=iymax)

regions/core/tests/test_bounding_box.py

@@ -99,3 +99,31 @@ def test_bounding_box_as_artist():
     assert_allclose(patch.get_xy(), (0.5, 1.5))
     assert_allclose(patch.get_width(), 9)
     assert_allclose(patch.get_height(), 18)
+
+def test_bounding_box_union():
+    bbox1 = BoundingBox(1, 10, 2, 20)
+    bbox2 = BoundingBox(5, 21, 7, 32)
+    bbox_union_expected = BoundingBox(1, 21, 2, 32)
+    bbox_union1 = bbox1 | bbox2
+    bbox_union2 = bbox1.union(bbox2)
+
+    assert bbox_union1 == bbox_union_expected
+    assert bbox_union1 == bbox_union2
+
+    with pytest.raises(TypeError):
+        bbox1.union((5, 21, 7, 32))
+
+def test_bounding_box_intersect():
+    bbox1 = BoundingBox(1, 10, 2, 20)
+    bbox2 = BoundingBox(5, 21, 7, 32)
+    bbox_intersect_expected = BoundingBox(5, 10, 7, 20)
+    bbox_intersect1 = bbox1 & bbox2
+    bbox_intersect2 = bbox1.intersection(bbox2)
+
+    assert bbox_intersect1 == bbox_intersect_expected
+    assert bbox_intersect1 == bbox_intersect2
+
+    with pytest.raises(TypeError):
+        bbox1.intersection((5, 21, 7, 32))
+
+    assert bbox1.intersection(BoundingBox(30, 40, 50, 60)) is None