add int -> int scaling setup for cvcuda, use bit diff for scale

Author: justincdavis

test/test_transforms_v2.py

@@ -2748,8 +2748,6 @@ def test_image_correctness(self, input_dtype, output_dtype, device, scale, make_
             pytest.xfail("float to int64 conversion is not supported")
         if input_dtype == torch.uint8 and output_dtype == torch.uint16 and device == "cuda":
             pytest.xfail("uint8 to uint16 conversion is not supported on cuda")
-        if input_dtype == torch.uint8 and output_dtype == torch.uint16 and scale and make_input == make_image_cvcuda:
-            pytest.xfail("uint8 to uint16 conversion with scale is not supported in F._misc._to_dtype_cvcuda")
 
         input = make_input(dtype=input_dtype, device=device)
         out = F.to_dtype(input, dtype=output_dtype, scale=scale)

torchvision/transforms/v2/functional/_misc.py

@@ -388,7 +388,9 @@ def _to_dtype_cvcuda(
             4. int -> float
             If scale is True, the values will be scaled to the new dtype.
             If scale is False, the values will not be scaled.
-            The scale values for float -> float and int -> int are 1.0 and 0.0 respectively.
+            The scale values for float -> float are 1.0 and 0.0 respectively.
+            The scale values for int -> int are 2^(bit_diff) of the new dtype.
+            Where bit_diff is the difference in the number of bits of the new dtype and the input dtype.
             The scale values for float -> int and int -> float are the maximum value of the new dtype.
 
     Returns:
@@ -405,8 +407,13 @@ def _to_dtype_cvcuda(
         in_dtype_float = dtype_in.is_floating_point
         out_dtype_float = dtype.is_floating_point
 
-        if in_dtype_float == out_dtype_float:
+        if in_dtype_float and out_dtype_float:
             scale_val, offset = 1.0, 0.0
+        elif not in_dtype_float and not out_dtype_float:
+            in_bits = torch.iinfo(dtype_in).bits
+            out_bits = torch.iinfo(dtype).bits
+            scale_val = float(2 ** (out_bits - in_bits))
+            offset = 0.0
         elif in_dtype_float and not out_dtype_float:
             scale_val, offset = float(_max_value(dtype)), 0.0
         else: