[prototype] Speed up `adjust_hue_image_tensor` (#6938)

* Performance optimization on adjust_hue_image_tensor

* handle ints

* Inplace logical ops

* Remove unnecessary casting.

* Fix linter.

torchvision/prototype/transforms/functional/_color.py

@@ -208,11 +208,10 @@ def _rgb_to_hsv(image: torch.Tensor) -> torch.Tensor:
 
     mask_maxc_neq_r = maxc != r
     mask_maxc_eq_g = maxc == g
-    mask_maxc_neq_g = ~mask_maxc_eq_g
 
-    hr = (bc - gc).mul_(~mask_maxc_neq_r)
-    hg = (2.0 + rc).sub_(bc).mul_(mask_maxc_eq_g & mask_maxc_neq_r)
-    hb = (4.0 + gc).sub_(rc).mul_(mask_maxc_neq_g & mask_maxc_neq_r)
+    hg = rc.add(2.0).sub_(bc).mul_(mask_maxc_eq_g & mask_maxc_neq_r)
+    hr = bc.sub_(gc).mul_(~mask_maxc_neq_r)
+    hb = gc.add_(4.0).sub_(rc).mul_(mask_maxc_neq_r.logical_and_(mask_maxc_eq_g.logical_not_()))
 
     h = hr.add_(hg).add_(hb)
     h = h.mul_(1.0 / 6.0).add_(1.0).fmod_(1.0)
@@ -221,14 +220,16 @@ def _rgb_to_hsv(image: torch.Tensor) -> torch.Tensor:
 
 def _hsv_to_rgb(img: torch.Tensor) -> torch.Tensor:
     h, s, v = img.unbind(dim=-3)
-    h6 = h * 6
+    h6 = h.mul(6)
     i = torch.floor(h6)
-    f = h6 - i
+    f = h6.sub_(i)
     i = i.to(dtype=torch.int32)
 
-    p = (v * (1.0 - s)).clamp_(0.0, 1.0)
-    q = (v * (1.0 - s * f)).clamp_(0.0, 1.0)
-    t = (v * (1.0 - s * (1.0 - f))).clamp_(0.0, 1.0)
+    sxf = s * f
+    one_minus_s = 1.0 - s
+    q = (1.0 - sxf).mul_(v).clamp_(0.0, 1.0)
+    t = sxf.add_(one_minus_s).mul_(v).clamp_(0.0, 1.0)
+    p = one_minus_s.mul_(v).clamp_(0.0, 1.0)
     i.remainder_(6)
 
     mask = i.unsqueeze(dim=-3) == torch.arange(6, device=i.device).view(-1, 1, 1)
@@ -238,7 +239,7 @@ def _hsv_to_rgb(img: torch.Tensor) -> torch.Tensor:
     a3 = torch.stack((p, p, t, v, v, q), dim=-3)
     a4 = torch.stack((a1, a2, a3), dim=-4)
 
-    return (a4.mul_(mask.to(dtype=img.dtype).unsqueeze(dim=-4))).sum(dim=-3)
+    return (a4.mul_(mask.unsqueeze(dim=-4))).sum(dim=-3)
 
 
 def adjust_hue_image_tensor(image: torch.Tensor, hue_factor: float) -> torch.Tensor:

torchvision/prototype/transforms/functional/_meta.py

@@ -164,6 +164,7 @@ def convert_format_bounding_box(
     if new_format == old_format:
         return bounding_box
 
+    # TODO: Add _xywh_to_cxcywh and _cxcywh_to_xywh to improve performance
     if old_format == BoundingBoxFormat.XYWH:
         bounding_box = _xywh_to_xyxy(bounding_box, inplace)
     elif old_format == BoundingBoxFormat.CXCYWH:

torchvision/prototype/transforms/functional/_type_conversion.py

-import unittest.mock
 from typing import Any, Dict, Tuple, Union
 
 import numpy as np
@@ -20,6 +19,8 @@ def decode_image_with_pil(encoded_image: torch.Tensor) -> features.Image:
 
 @torch.jit.unused
 def decode_video_with_av(encoded_video: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor, Dict[str, Any]]:
+    import unittest.mock
+
     with unittest.mock.patch("torchvision.io.video.os.path.exists", return_value=True):
         return read_video(ReadOnlyTensorBuffer(encoded_video))  # type: ignore[arg-type]