Check num of channels on adjust_* transformations (#3069)

* Fixing upperbound value on tests and documentation.

* Limit the number of channels on adjust_* transoforms.

test/common_utils.py

@@ -339,13 +339,13 @@ def freeze_rng_state():
 class TransformsTester(unittest.TestCase):
 
     def _create_data(self, height=3, width=3, channels=3, device="cpu"):
-        tensor = torch.randint(0, 255, (channels, height, width), dtype=torch.uint8, device=device)
+        tensor = torch.randint(0, 256, (channels, height, width), dtype=torch.uint8, device=device)
         pil_img = Image.fromarray(tensor.permute(1, 2, 0).contiguous().cpu().numpy())
         return tensor, pil_img
 
     def _create_data_batch(self, height=3, width=3, channels=3, num_samples=4, device="cpu"):
         batch_tensor = torch.randint(
-            0, 255,
+            0, 256,
             (num_samples, channels, height, width),
             dtype=torch.uint8,
             device=device

torchvision/transforms/functional_tensor.py

@@ -1,5 +1,5 @@
 import warnings
-from typing import Optional, Dict, Tuple
+from typing import Optional, Tuple
 
 import torch
 from torch import Tensor
@@ -45,6 +45,12 @@ def _max_value(dtype: torch.dtype) -> float:
     return max_value.item()
 
 
+def _assert_channels(img: Tensor, permitted: List[int]) -> None:
+    c = _get_image_num_channels(img)
+    if c not in permitted:
+        raise TypeError("Input image tensor permitted channel values are {}, but found {}".format(permitted, c))
+
+
 def convert_image_dtype(image: torch.Tensor, dtype: torch.dtype = torch.float) -> torch.Tensor:
     """PRIVATE METHOD. Convert a tensor image to the given ``dtype`` and scale the values accordingly
 
@@ -210,9 +216,7 @@ def rgb_to_grayscale(img: Tensor, num_output_channels: int = 1) -> Tensor:
     """
     if img.ndim < 3:
         raise TypeError("Input image tensor should have at least 3 dimensions, but found {}".format(img.ndim))
-    c = img.shape[-3]
-    if c != 3:
-        raise TypeError("Input image tensor should 3 channels, but found {}".format(c))
+    _assert_channels(img, [3])
 
     if num_output_channels not in (1, 3):
         raise ValueError('num_output_channels should be either 1 or 3')
@@ -230,7 +234,7 @@ def rgb_to_grayscale(img: Tensor, num_output_channels: int = 1) -> Tensor:
 
 
 def adjust_brightness(img: Tensor, brightness_factor: float) -> Tensor:
-    """PRIVATE METHOD. Adjust brightness of an RGB image.
+    """PRIVATE METHOD. Adjust brightness of a Grayscale or RGB image.
 
     .. warning::
 
@@ -252,6 +256,8 @@ def adjust_brightness(img: Tensor, brightness_factor: float) -> Tensor:
     if not _is_tensor_a_torch_image(img):
         raise TypeError('tensor is not a torch image.')
 
+    _assert_channels(img, [1, 3])
+
     return _blend(img, torch.zeros_like(img), brightness_factor)
 
 
@@ -278,14 +284,16 @@ def adjust_contrast(img: Tensor, contrast_factor: float) -> Tensor:
     if not _is_tensor_a_torch_image(img):
         raise TypeError('tensor is not a torch image.')
 
+    _assert_channels(img, [3])
+
     dtype = img.dtype if torch.is_floating_point(img) else torch.float32
     mean = torch.mean(rgb_to_grayscale(img).to(dtype), dim=(-3, -2, -1), keepdim=True)
 
     return _blend(img, mean, contrast_factor)
 
 
 def adjust_hue(img: Tensor, hue_factor: float) -> Tensor:
-    """PRIVATE METHOD. Adjust hue of an image.
+    """PRIVATE METHOD. Adjust hue of an RGB image.
 
     .. warning::
 
@@ -320,6 +328,8 @@ def adjust_hue(img: Tensor, hue_factor: float) -> Tensor:
     if not (isinstance(img, torch.Tensor) and _is_tensor_a_torch_image(img)):
         raise TypeError('Input img should be Tensor image')
 
+    _assert_channels(img, [3])
+
     orig_dtype = img.dtype
     if img.dtype == torch.uint8:
         img = img.to(dtype=torch.float32) / 255.0
@@ -359,11 +369,13 @@ def adjust_saturation(img: Tensor, saturation_factor: float) -> Tensor:
     if not _is_tensor_a_torch_image(img):
         raise TypeError('tensor is not a torch image.')
 
+    _assert_channels(img, [3])
+
     return _blend(img, rgb_to_grayscale(img), saturation_factor)
 
 
 def adjust_gamma(img: Tensor, gamma: float, gain: float = 1) -> Tensor:
-    r"""PRIVATE METHOD. Adjust gamma of an RGB image.
+    r"""PRIVATE METHOD. Adjust gamma of a Grayscale or RGB image.
 
     .. warning::
 
@@ -391,6 +403,8 @@ def adjust_gamma(img: Tensor, gamma: float, gain: float = 1) -> Tensor:
     if not isinstance(img, torch.Tensor):
         raise TypeError('Input img should be a Tensor.')
 
+    _assert_channels(img, [1, 3])
+
     if gamma < 0:
         raise ValueError('Gamma should be a non-negative real number')