Add box_area_center and box_iou_center for cxcywh format

Author: alperenunlu

docs/source/ops.rst

@@ -50,8 +50,10 @@ These utility functions perform various operations on bounding boxes.
     :template: function.rst
 
     box_area
+    box_area_center
     box_convert
     box_iou
+    box_iou_center
     clip_boxes_to_image
     complete_box_iou
     distance_box_iou

test/test_ops.py

@@ -1451,6 +1451,41 @@ def test_box_area_jit(self):
         torch.testing.assert_close(scripted_area, expected)
 
 
+class TestBoxAreaCenter:
+    def area_check(self, box, expected, atol=1e-4):
+        out = ops.box_area_center(box)
+        torch.testing.assert_close(out, expected, rtol=0.0, check_dtype=False, atol=atol)
+
+    @pytest.mark.parametrize("dtype", [torch.int8, torch.int16, torch.int32, torch.int64])
+    def test_int_boxes(self, dtype):
+        box_tensor = ops.box_convert(torch.tensor([[0, 0, 100, 100], [0, 0, 0, 0]], dtype=dtype),
+                                     in_fmt="xyxy", out_fmt="cxcywh")
+        expected = torch.tensor([10000, 0], dtype=torch.int32)
+        self.area_check(box_tensor, expected)
+
+    @pytest.mark.parametrize("dtype", [torch.float32, torch.float64])
+    def test_float_boxes(self, dtype):
+        box_tensor = ops.box_convert(torch.tensor(FLOAT_BOXES, dtype=dtype), in_fmt="xyxy", out_fmt="cxcywh")
+        expected = torch.tensor([604723.0806, 600965.4666, 592761.0085], dtype=dtype)
+        self.area_check(box_tensor, expected)
+
+    def test_float16_box(self):
+        box_tensor = ops.box_convert(torch.tensor(
+            [[2.825, 1.8625, 3.90, 4.85], [2.825, 4.875, 19.20, 5.10], [2.925, 1.80, 8.90, 4.90]], dtype=torch.float16
+        ), in_fmt="xyxy", out_fmt="cxcywh")
+
+        expected = torch.tensor([3.2170, 3.7108, 18.5071], dtype=torch.float16)
+        self.area_check(box_tensor, expected, atol=0.01)
+
+    def test_box_area_jit(self):
+        box_tensor = ops.box_convert(torch.tensor([[0, 0, 100, 100], [0, 0, 0, 0]], dtype=torch.float),
+                                     in_fmt="xyxy", out_fmt="cxcywh")
+        expected = ops.box_area_center(box_tensor)
+        scripted_fn = torch.jit.script(ops.box_area_center)
+        scripted_area = scripted_fn(box_tensor)
+        torch.testing.assert_close(scripted_area, expected)
+
+
 INT_BOXES = [[0, 0, 100, 100], [0, 0, 50, 50], [200, 200, 300, 300], [0, 0, 25, 25]]
 INT_BOXES2 = [[0, 0, 100, 100], [0, 0, 50, 50], [200, 200, 300, 300]]
 FLOAT_BOXES = [
@@ -1459,6 +1494,14 @@ def test_box_area_jit(self):
     [279.2440, 197.9812, 1189.4746, 849.2019],
 ]
 
+INT_BOXES_CXCYWH = [[50, 50, 100, 100], [25, 25, 50, 50], [250, 250, 100, 100], [10, 10, 20, 20]]
+INT_BOXES2_CXCYWH = [[50, 50, 100, 100], [25, 25, 50, 50], [250, 250, 100, 100]]
+FLOAT_BOXES_CXCYWH = [
+    [739.4324, 518.5154, 908.1572, 665.8793],
+    [738.8228, 519.9021, 907.3512, 662.3295],
+    [734.3593, 523.5916, 910.2306, 651.2207]
+]
+
 
 def gen_box(size, dtype=torch.float):
     xy1 = torch.rand((size, 2), dtype=dtype)
@@ -1525,6 +1568,65 @@ def test_iou_cartesian(self):
         self._run_cartesian_test(ops.box_iou)
 
 
+class TestIouCenterBase:
+    @staticmethod
+    def _run_test(target_fn: Callable, actual_box1, actual_box2, dtypes, atol, expected):
+        for dtype in dtypes:
+            actual_box1 = torch.tensor(actual_box1, dtype=dtype)
+            actual_box2 = torch.tensor(actual_box2, dtype=dtype)
+            expected_box = torch.tensor(expected)
+            out = target_fn(actual_box1, actual_box2)
+            torch.testing.assert_close(out, expected_box, rtol=0.0, check_dtype=False, atol=atol)
+
+    @staticmethod
+    def _run_jit_test(target_fn: Callable, actual_box: List):
+        box_tensor = torch.tensor(actual_box, dtype=torch.float)
+        expected = target_fn(box_tensor, box_tensor)
+        scripted_fn = torch.jit.script(target_fn)
+        scripted_out = scripted_fn(box_tensor, box_tensor)
+        torch.testing.assert_close(scripted_out, expected)
+
+    @staticmethod
+    def _cartesian_product(boxes1, boxes2, target_fn: Callable):
+        N = boxes1.size(0)
+        M = boxes2.size(0)
+        result = torch.zeros((N, M))
+        for i in range(N):
+            for j in range(M):
+                result[i, j] = target_fn(boxes1[i].unsqueeze(0), boxes2[j].unsqueeze(0))
+        return result
+
+    @staticmethod
+    def _run_cartesian_test(target_fn: Callable):
+        boxes1 = ops.box_convert(gen_box(5), in_fmt="xyxy", out_fmt="cxcywh")
+        boxes2 = ops.box_convert(gen_box(7), in_fmt="xyxy", out_fmt="cxcywh")
+        a = TestIouCenterBase._cartesian_product(boxes1, boxes2, target_fn)
+        b = target_fn(boxes1, boxes2)
+        torch.testing.assert_close(a, b)
+
+
+class TestBoxIouCenter(TestIouBase):
+    int_expected = [[1.0, 0.25, 0.0], [0.25, 1.0, 0.0], [0.0, 0.0, 1.0], [0.04, 0.16, 0.0]]
+    float_expected = [[1.0, 0.9933, 0.9673], [0.9933, 1.0, 0.9737], [0.9673, 0.9737, 1.0]]
+
+    @pytest.mark.parametrize(
+        "actual_box1, actual_box2, dtypes, atol, expected",
+        [
+            pytest.param(INT_BOXES_CXCYWH, INT_BOXES2_CXCYWH, [torch.int16, torch.int32, torch.int64], 1e-4, int_expected),
+            pytest.param(FLOAT_BOXES_CXCYWH, FLOAT_BOXES_CXCYWH, [torch.float16], 0.002, float_expected),
+            pytest.param(FLOAT_BOXES_CXCYWH, FLOAT_BOXES_CXCYWH, [torch.float32, torch.float64], 1e-3, float_expected),
+        ],
+    )
+    def test_iou(self, actual_box1, actual_box2, dtypes, atol, expected):
+        self._run_test(ops.box_iou_center, actual_box1, actual_box2, dtypes, atol, expected)
+
+    def test_iou_jit(self):
+        self._run_jit_test(ops.box_iou_center, INT_BOXES_CXCYWH)
+
+    def test_iou_cartesian(self):
+        self._run_cartesian_test(ops.box_iou_center)
+
+
 class TestGeneralizedBoxIou(TestIouBase):
     int_expected = [[1.0, 0.25, -0.7778], [0.25, 1.0, -0.8611], [-0.7778, -0.8611, 1.0], [0.0625, 0.25, -0.8819]]
     float_expected = [[1.0, 0.9933, 0.9673], [0.9933, 1.0, 0.9737], [0.9673, 0.9737, 1.0]]

torchvision/ops/__init__.py

@@ -2,8 +2,10 @@
 from .boxes import (
     batched_nms,
     box_area,
+    box_area_center,
     box_convert,
     box_iou,
+    box_iou_center,
     clip_boxes_to_image,
     complete_box_iou,
     distance_box_iou,
@@ -40,7 +42,9 @@
     "clip_boxes_to_image",
     "box_convert",
     "box_area",
+    "box_area_center",
     "box_iou",
+    "box_iou_center",
     "generalized_box_iou",
     "distance_box_iou",
     "complete_box_iou",

torchvision/ops/boxes.py

@@ -290,6 +290,25 @@ def box_area(boxes: Tensor) -> Tensor:
     return (boxes[:, 2] - boxes[:, 0]) * (boxes[:, 3] - boxes[:, 1])
 
 
+def box_area_center(boxes: Tensor) -> Tensor:
+    """
+    Computes the area of a set of bounding boxes, which are specified by their
+    (cx, cy, w, h) coordinates.
+
+    Args:
+        boxes (Tensor[N, 4]): boxes for which the area will be computed. They
+            are expected to be in (cx, cy, w, h) format with
+            ``0 <= cx``, ``0 <= cy``, ``0 <= w`` and ``0 <= h``.
+
+    Returns:
+        Tensor[N]: the area for each box
+    """
+    if not torch.jit.is_scripting() and not torch.jit.is_tracing():
+        _log_api_usage_once(box_area)
+    boxes = _upcast(boxes)
+    return boxes[:, 2] * boxes[:, 3]
+
+
 # implementation from https://github.com/kuangliu/torchcv/blob/master/torchcv/utils/box.py
 # with slight modifications
 def _box_inter_union(boxes1: Tensor, boxes2: Tensor) -> Tuple[Tensor, Tensor]:
@@ -328,6 +347,42 @@ def box_iou(boxes1: Tensor, boxes2: Tensor) -> Tensor:
     return iou
 
 
+def _box_inter_union_center(boxes1: Tensor, boxes2: Tensor) -> Tuple[Tensor, Tensor]:
+    area1 = box_area_center(boxes1)
+    area2 = box_area_center(boxes2)
+
+    lt = torch.max(boxes1[:, None, :2] - boxes1[:, None, 2:] / 2, boxes2[:, :2] - boxes2[:, 2:] / 2)  # [N,M,2]
+    rb = torch.min(boxes1[:, None, :2] + boxes1[:, None, 2:] / 2, boxes2[:, :2] + boxes2[:, 2:] / 2)  # [N,M,2]
+
+    wh = _upcast(rb - lt).clamp(min=0)  # [N,M,2]
+    inter = wh[:, :, 0] * wh[:, :, 1]  # [N,M]
+
+    union = area1[:, None] + area2 - inter
+
+    return inter, union
+
+
+def box_iou_center(boxes1: Tensor, boxes2: Tensor) -> Tensor:
+    """
+    Return intersection-over-union (Jaccard index) between two sets of boxes.
+
+    Both sets of boxes are expected to be in ``(cx, cy, w, h)`` format with
+    ``0 <= cx``, ``0 <= cy``, ``0 <= w`` and ``0 <= h``.
+
+    Args:
+        boxes1 (Tensor[N, 4]): first set of boxes
+        boxes2 (Tensor[M, 4]): second set of boxes
+
+    Returns:
+        Tensor[N, M]: the NxM matrix containing the pairwise IoU values for every element in boxes1 and boxes2
+    """
+    if not torch.jit.is_scripting() and not torch.jit.is_tracing():
+        _log_api_usage_once(box_iou_center)
+    inter, union = _box_inter_union_center(boxes1, boxes2)
+    iou = inter / union
+    return iou
+
+
 # Implementation adapted from https://github.com/facebookresearch/detr/blob/master/util/box_ops.py
 def generalized_box_iou(boxes1: Tensor, boxes2: Tensor) -> Tensor:
     """