DM-51670: Add bbox property to BlendData classes

python/lsst/scarlet/lite/io/blend.py

@@ -2,6 +2,7 @@
 
 import logging
 from dataclasses import dataclass
+from functools import cached_property
 from typing import Any
 
 import numpy as np
@@ -51,6 +52,11 @@ class ScarletBlendData(ScarletBlendBaseData):
     sources: dict[Any, ScarletSourceBaseData]
     version: str = CURRENT_SCHEMA
 
+    @cached_property
+    def bbox(self) -> Box:
+        """The bounding box of the blend"""
+        return Box(self.shape, origin=self.origin)
+
     def as_dict(self) -> dict:
         """Return the object encoded into a dict for JSON serialization
 
@@ -131,7 +137,7 @@ def minimal_data_to_blend(
         _model_psf: np.ndarray = extract_from_metadata(model_psf, self.metadata, "model_psf")
         _psf: np.ndarray = extract_from_metadata(psf, self.metadata, "psf")
         _bands: tuple[str] = extract_from_metadata(bands, self.metadata, "bands")
-        model_box = Box(self.shape, origin=self.origin)
+        model_box = self.bbox
         observation = Observation.empty(
             bands=_bands,
             psfs=_psf,

python/lsst/scarlet/lite/io/blend_base.py

@@ -6,6 +6,7 @@
 
 from numpy.typing import DTypeLike
 
+from ..bbox import Box
 from .utils import PersistenceError
 
 __all__ = ["ScarletBlendBaseData"]
@@ -32,6 +33,11 @@ class ScarletBlendBaseData(ABC):
     metadata: dict[str, Any] | None = None
     version: str
 
+    @property
+    @abstractmethod
+    def bbox(self) -> Box:
+        """The bounding box of the blend"""
+
     @classmethod
     def register(cls) -> None:
         """Register a new Blend type"""

python/lsst/scarlet/lite/io/hierarchical_blend.py

@@ -6,6 +6,7 @@
 import numpy as np
 from numpy.typing import DTypeLike
 
+from ..bbox import Box
 from .blend_base import ScarletBlendBaseData
 from .migration import PRE_SCHEMA, MigrationRegistry, migration
 from .utils import PersistenceError, decode_metadata, encode_metadata
@@ -35,6 +36,21 @@ class HierarchicalBlendData(ScarletBlendBaseData):
     children: dict[int, ScarletBlendBaseData]
     version: str = CURRENT_SCHEMA
 
+    @property
+    def bbox(self) -> Box:
+        """The bounding box of the blend"""
+        # Compute the bounding box that contains all children
+        if not self.children:
+            raise ValueError("HierarchicalBlendData has no children to compute bbox from.")
+        bboxes = [child.bbox for child in self.children.values()]
+        min_y = min(bbox.origin[0] for bbox in bboxes)
+        min_x = min(bbox.origin[1] for bbox in bboxes)
+        max_y = max(bbox.origin[0] + bbox.shape[0] for bbox in bboxes)
+        max_x = max(bbox.origin[1] + bbox.shape[1] for bbox in bboxes)
+        origin = (min_y, min_x)
+        shape = (max_y - min_y, max_x - min_x)
+        return Box(shape, origin=origin)
+
     def as_dict(self) -> dict:
         """Return the object encoded into a dict for JSON serialization
 

tests/test_io.py

@@ -85,6 +85,7 @@ def test_json(self):
         self.assertEqual(len(blend.sources), len(loaded_blend.sources))
         self.assertEqual(len(blend.components), len(loaded_blend.components))
         self.assertImageAlmostEqual(blend.get_model(), loaded_blend.get_model())
+        self.assertBoxEqual(blend.bbox, blend_data.bbox)
 
         for sidx in range(len(blend.sources)):
             source1 = blend.sources[sidx]