[enhance] improve flipping and cropping speed (kornia#2179)

* init

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* restore wrong file

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

kornia/augmentation/_2d/geometric/crop.py

@@ -140,7 +140,8 @@ def precrop_padding(
         if padding is None:
             padding = self.compute_padding(input.shape)
 
-        input = pad(input, padding, value=flags["fill"], mode=flags["padding_mode"])
+        if any(padding):
+            input = pad(input, padding, value=flags["fill"], mode=flags["padding_mode"])
 
         return input
 

kornia/geometry/transform/flips.py

@@ -124,8 +124,7 @@ def hflip(input: Tensor) -> Tensor:
     Returns:
         The horizontally flipped image tensor.
     """
-    w = input.shape[-1]
-    return input[..., torch.arange(w - 1, -1, -1, device=input.device)]
+    return input.flip(-1).contiguous()
 
 
 def vflip(input: Tensor) -> Tensor:
@@ -141,5 +140,4 @@ def vflip(input: Tensor) -> Tensor:
     Returns:
         The vertically flipped image tensor.
     """
-    h = input.shape[-2]
-    return input[..., torch.arange(h - 1, -1, -1, device=input.device), :]
+    return input.flip(-2).contiguous()