From a7680b4f0787037186764bbb1ba4a2b77f561f7f Mon Sep 17 00:00:00 2001
From: Josh Veitch-Michaelis <j.veitchmichaelis@gmail.com>
Date: Sat, 24 Jan 2026 16:50:46 -0500
Subject: [PATCH] support coco bbox format

---
 src/deepforest/utilities.py | 37 ++++++++++++++++++++-----------
 tests/test_utilities.py     | 43 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 66 insertions(+), 14 deletions(-)

diff --git a/src/deepforest/utilities.py b/src/deepforest/utilities.py
index f467bbc6c..434caf8ab 100644
--- a/src/deepforest/utilities.py
+++ b/src/deepforest/utilities.py
@@ -416,7 +416,7 @@ def format_boxes(prediction, scores=True):
     return df
 
 
-def read_coco(json_file):
+def read_coco(json_file, mode="box"):
     """Read a COCO format JSON file and return a pandas dataframe.
 
     Args:
@@ -439,18 +439,29 @@ def read_coco(json_file):
     filenames = []
     labels = []
 
+    # Format reference: https://cocodataset.org/#format-data
     for annotation in coco_data["annotations"]:
-        segmentation = annotation.get("segmentation")
-        if not segmentation:
-            continue
-        # COCO polygons are usually a list of lists; take the first (assume "single part")
-        segmentation_mask = segmentation[0]
-        # Convert flat list to coordinate pairs
-        pairs = [
-            (segmentation_mask[i], segmentation_mask[i + 1])
-            for i in range(0, len(segmentation_mask), 2)
-        ]
-        polygon = shapely.geometry.Polygon(pairs)
+        if mode == "box":
+            # COCO bbox format is [x, y, width, height]
+            x, y, width, height = annotation["bbox"]
+            # Shapely box format is [minx, miny, maxx, maxy]
+            polygon = shapely.box(x, y, x + width, y + height)
+        elif mode == "segm":
+            # COCO polygons are usually a list of lists; take the first (assume "single part")
+            segmentation = annotation.get("segmentation")
+            if not segmentation or len(segmentation) == 0:
+                continue
+
+            segmentation_mask = segmentation[0]
+            # Convert flat list to coordinate pairs
+            pairs = [
+                (segmentation_mask[i], segmentation_mask[i + 1])
+                for i in range(0, len(segmentation_mask), 2)
+            ]
+            polygon = shapely.geometry.Polygon(pairs)
+        elif mode == "keypoint":
+            raise NotImplementedError
+
         filenames.append(image_ids[annotation["image_id"]])
         polygons.append(polygon.wkt)
         cat_id = annotation.get("category_id")
@@ -578,7 +589,7 @@ def read_file(
             df = pd.read_csv(input)
             gdf = _pandas_to_deepforest_format__(input, df, image_path, root_dir, label)
         elif input.endswith(".json"):
-            df = read_coco(input)
+            df = read_coco(input, mode="box")
             gdf = _pandas_to_deepforest_format__(input, df, image_path, root_dir, label)
         elif input.endswith(".xml"):
             df = read_pascal_voc(input)
diff --git a/tests/test_utilities.py b/tests/test_utilities.py
index 0be8a665b..687e1150d 100644
--- a/tests/test_utilities.py
+++ b/tests/test_utilities.py
@@ -558,7 +558,7 @@ def test_image_to_geo_coordinates_polygons():
 
 
 
-def test_read_coco_json(tmp_path):
+def test_read_coco_json_polygon(tmp_path):
     """Test reading a COCO format JSON file"""
     # Create a sample COCO JSON structure
     coco_data = {
@@ -608,6 +608,47 @@ def test_read_coco_json(tmp_path):
         assert geom.is_valid
         assert isinstance(geom, shapely.geometry.Polygon)
 
+def test_read_coco_json_bbox(tmp_path):
+    """Test reading a COCO format JSON file"""
+    # Create a sample COCO JSON structure
+    coco_data = {
+        "images": [
+            {"id": 1, "file_name": "OSBS_029.png"},
+            {"id": 2, "file_name": "OSBS_029.tif"}
+        ],
+        "categories": [
+            {"id": 0, "name": "Tree"},
+            {"id": 1, "name": "Bird"}
+        ],
+        "annotations": [
+            {
+                "image_id": 1,
+                "bbox": [0, 0, 10, 10],  # x, y, width, height
+                "category_id": 0
+            },
+            {
+                "image_id": 2,
+                "bbox": [5, 5, 10, 10],
+                "category_id": 1
+            }
+        ]
+    }
+
+    # Write the sample JSON to a temporary file
+    json_path = tmp_path / "annotations.json"
+    with open(json_path, "w") as f:
+        json.dump(coco_data, f)
+
+    # Read the file using our utility
+    df = utilities.read_file(str(json_path), root_dir=os.path.dirname(get_data("OSBS_029.png")))
+
+    # Assert the dataframe has the expected structure
+    assert df.shape[0] == 2  # Two annotations
+
+    # Check bboxes:
+    expected_boxes = [geometry.box(0, 0, 10, 10), geometry.box(5, 5, 15, 15)]
+    for geom, expected in zip(df.geometry, expected_boxes):
+        assert geom.equals(expected)
 
 def test_format_geometry_box():
     """Test formatting box geometry from model predictions"""