add float support to `utils.draw_bounding_boxes()` (#8328)

Co-authored-by: Nicolas Hug <nh.nicolas.hug@gmail.com>
Co-authored-by: Nicolas Hug <contact@nicolas-hug.com>

test/test_utils.py

@@ -116,6 +116,23 @@ def test_draw_boxes():
     assert_equal(img, img_cp)
 
 
+@pytest.mark.parametrize("fill", [True, False])
+def test_draw_boxes_dtypes(fill):
+    img_uint8 = torch.full((3, 100, 100), 255, dtype=torch.uint8)
+    out_uint8 = utils.draw_bounding_boxes(img_uint8, boxes, fill=fill)
+
+    assert img_uint8 is not out_uint8
+    assert out_uint8.dtype == torch.uint8
+
+    img_float = to_dtype(img_uint8, torch.float, scale=True)
+    out_float = utils.draw_bounding_boxes(img_float, boxes, fill=fill)
+
+    assert img_float is not out_float
+    assert out_float.is_floating_point()
+
+    torch.testing.assert_close(out_uint8, to_dtype(out_float, torch.uint8, scale=True), rtol=0, atol=1)
+
+
 @pytest.mark.parametrize("colors", [None, ["red", "blue", "#FF00FF", (1, 34, 122)], "red", "#FF00FF", (1, 34, 122)])
 def test_draw_boxes_colors(colors):
     img = torch.full((3, 100, 100), 0, dtype=torch.uint8)
@@ -152,7 +169,6 @@ def test_draw_boxes_grayscale():
 
 def test_draw_invalid_boxes():
     img_tp = ((1, 1, 1), (1, 2, 3))
-    img_wrong1 = torch.full((3, 5, 5), 255, dtype=torch.float)
     img_wrong2 = torch.full((1, 3, 5, 5), 255, dtype=torch.uint8)
     img_correct = torch.zeros((3, 10, 10), dtype=torch.uint8)
     boxes = torch.tensor([[0, 0, 20, 20], [0, 0, 0, 0], [10, 15, 30, 35], [23, 35, 93, 95]], dtype=torch.float)
@@ -162,8 +178,6 @@ def test_draw_invalid_boxes():
 
     with pytest.raises(TypeError, match="Tensor expected"):
         utils.draw_bounding_boxes(img_tp, boxes)
-    with pytest.raises(ValueError, match="Tensor uint8 expected"):
-        utils.draw_bounding_boxes(img_wrong1, boxes)
     with pytest.raises(ValueError, match="Pass individual images, not batches"):
         utils.draw_bounding_boxes(img_wrong2, boxes)
     with pytest.raises(ValueError, match="Only grayscale and RGB images are supported"):

torchvision/utils.py

@@ -164,12 +164,12 @@ def draw_bounding_boxes(
 ) -> torch.Tensor:
 
     """
-    Draws bounding boxes on given image.
-    The values of the input image should be uint8 between 0 and 255.
+    Draws bounding boxes on given RGB image.
+    The image values should be uint8 in [0, 255] or float in [0, 1].
     If fill is True, Resulting Tensor should be saved as PNG image.
 
     Args:
-        image (Tensor): Tensor of shape (C x H x W) and dtype uint8.
+        image (Tensor): Tensor of shape (C, H, W) and dtype uint8 or float.
         boxes (Tensor): Tensor of size (N, 4) containing bounding boxes in (xmin, ymin, xmax, ymax) format. Note that
             the boxes are absolute coordinates with respect to the image. In other words: `0 <= xmin < xmax < W` and
             `0 <= ymin < ymax < H`.
@@ -188,13 +188,14 @@ def draw_bounding_boxes(
     Returns:
         img (Tensor[C, H, W]): Image Tensor of dtype uint8 with bounding boxes plotted.
     """
+    import torchvision.transforms.v2.functional as F  # noqa
 
     if not torch.jit.is_scripting() and not torch.jit.is_tracing():
         _log_api_usage_once(draw_bounding_boxes)
     if not isinstance(image, torch.Tensor):
         raise TypeError(f"Tensor expected, got {type(image)}")
-    elif image.dtype != torch.uint8:
-        raise ValueError(f"Tensor uint8 expected, got {image.dtype}")
+    elif not (image.dtype == torch.uint8 or image.is_floating_point()):
+        raise ValueError(f"The image dtype must be uint8 or float, got {image.dtype}")
     elif image.dim() != 3:
         raise ValueError("Pass individual images, not batches")
     elif image.size(0) not in {1, 3}:
@@ -230,8 +231,11 @@ def draw_bounding_boxes(
     if image.size(0) == 1:
         image = torch.tile(image, (3, 1, 1))
 
-    ndarr = image.permute(1, 2, 0).cpu().numpy()
-    img_to_draw = Image.fromarray(ndarr)
+    original_dtype = image.dtype
+    if original_dtype.is_floating_point:
+        image = F.to_dtype(image, dtype=torch.uint8, scale=True)
+
+    img_to_draw = F.to_pil_image(image)
     img_boxes = boxes.to(torch.int64).tolist()
 
     if fill:
@@ -250,7 +254,10 @@ def draw_bounding_boxes(
             margin = width + 1
             draw.text((bbox[0] + margin, bbox[1] + margin), label, fill=color, font=txt_font)
 
-    return torch.from_numpy(np.array(img_to_draw)).permute(2, 0, 1).to(dtype=torch.uint8)
+    out = F.pil_to_tensor(img_to_draw)
+    if original_dtype.is_floating_point:
+        out = F.to_dtype(out, dtype=original_dtype, scale=True)
+    return out
 
 
 @torch.no_grad()