Open Doc nits in image decoding functions (#4681)

torchvision/io/image.py

@@ -59,7 +59,7 @@ def write_file(filename: str, data: torch.Tensor) -> None:
 
 def decode_png(input: torch.Tensor, mode: ImageReadMode = ImageReadMode.UNCHANGED) -> torch.Tensor:
     """
-    Decodes a PNG image into a 3 dimensional RGB Tensor.
+    Decodes a PNG image into a 3 dimensional RGB or grayscale Tensor.
     Optionally converts the image to the desired format.
     The values of the output tensor are uint8 between 0 and 255.
 
@@ -117,7 +117,7 @@ def decode_jpeg(
     input: torch.Tensor, mode: ImageReadMode = ImageReadMode.UNCHANGED, device: str = "cpu"
 ) -> torch.Tensor:
     """
-    Decodes a JPEG image into a 3 dimensional RGB Tensor.
+    Decodes a JPEG image into a 3 dimensional RGB or grayscale Tensor.
     Optionally converts the image to the desired format.
     The values of the output tensor are uint8 between 0 and 255.
 
@@ -185,7 +185,7 @@ def write_jpeg(input: torch.Tensor, filename: str, quality: int = 75):
 def decode_image(input: torch.Tensor, mode: ImageReadMode = ImageReadMode.UNCHANGED) -> torch.Tensor:
     """
     Detects whether an image is a JPEG or PNG and performs the appropriate
-    operation to decode the image into a 3 dimensional RGB Tensor.
+    operation to decode the image into a 3 dimensional RGB or grayscale Tensor.
 
     Optionally converts the image to the desired format.
     The values of the output tensor are uint8 between 0 and 255.
@@ -207,7 +207,7 @@ def decode_image(input: torch.Tensor, mode: ImageReadMode = ImageReadMode.UNCHAN
 
 def read_image(path: str, mode: ImageReadMode = ImageReadMode.UNCHANGED) -> torch.Tensor:
     """
-    Reads a JPEG or PNG image into a 3 dimensional RGB Tensor.
+    Reads a JPEG or PNG image into a 3 dimensional RGB or grayscale Tensor.
     Optionally converts the image to the desired format.
     The values of the output tensor are uint8 between 0 and 255.