Added typing annotations to transforms/functional_pil (#4234)

* fix

* add functional PIL typings

* fix types

* fix types

* fix a small one

* small fix

* fix type

* fix interpolation types
Co-authored-by: Vasilis Vryniotis <datumbox@users.noreply.github.com>

torchvision/transforms/functional_pil.py

 import numbers
-from typing import Any, List, Sequence
+from typing import Any, Dict, List, Optional, Sequence, Tuple, Union
 
 import numpy as np
 import torch
@@ -34,7 +34,7 @@ def _get_image_num_channels(img: Any) -> int:
 
 
 @torch.jit.unused
-def hflip(img):
+def hflip(img: Image.Image) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -42,7 +42,7 @@ def hflip(img):
 
 
 @torch.jit.unused
-def vflip(img):
+def vflip(img: Image.Image) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -50,7 +50,7 @@ def vflip(img):
 
 
 @torch.jit.unused
-def adjust_brightness(img, brightness_factor):
+def adjust_brightness(img: Image.Image, brightness_factor: float) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -60,7 +60,7 @@ def adjust_brightness(img, brightness_factor):
 
 
 @torch.jit.unused
-def adjust_contrast(img, contrast_factor):
+def adjust_contrast(img: Image.Image, contrast_factor: float) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -70,7 +70,7 @@ def adjust_contrast(img, contrast_factor):
 
 
 @torch.jit.unused
-def adjust_saturation(img, saturation_factor):
+def adjust_saturation(img: Image.Image, saturation_factor: float) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -80,7 +80,7 @@ def adjust_saturation(img, saturation_factor):
 
 
 @torch.jit.unused
-def adjust_hue(img, hue_factor):
+def adjust_hue(img: Image.Image, hue_factor: float) -> Image.Image:
     if not(-0.5 <= hue_factor <= 0.5):
         raise ValueError('hue_factor ({}) is not in [-0.5, 0.5].'.format(hue_factor))
 
@@ -104,7 +104,12 @@ def adjust_hue(img, hue_factor):
 
 
 @torch.jit.unused
-def adjust_gamma(img, gamma, gain=1):
+def adjust_gamma(
+    img: Image.Image,
+    gamma: float,
+    gain: float = 1.0,
+) -> Image.Image:
+
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -121,7 +126,13 @@ def adjust_gamma(img, gamma, gain=1):
 
 
 @torch.jit.unused
-def pad(img, padding, fill=0, padding_mode="constant"):
+def pad(
+    img: Image.Image,
+    padding: Union[int, List[int], Tuple[int, ...]],
+    fill: Optional[Union[float, List[float], Tuple[float, ...]]] = 0,
+    padding_mode: str = "constant",
+) -> Image.Image:
+
     if not _is_pil_image(img):
         raise TypeError("img should be PIL Image. Got {}".format(type(img)))
 
@@ -196,7 +207,14 @@ def pad(img, padding, fill=0, padding_mode="constant"):
 
 
 @torch.jit.unused
-def crop(img: Image.Image, top: int, left: int, height: int, width: int) -> Image.Image:
+def crop(
+    img: Image.Image,
+    top: int,
+    left: int,
+    height: int,
+    width: int,
+) -> Image.Image:
+
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -204,7 +222,13 @@ def crop(img: Image.Image, top: int, left: int, height: int, width: int) -> Imag
 
 
 @torch.jit.unused
-def resize(img, size, interpolation=Image.BILINEAR, max_size=None):
+def resize(
+    img: Image.Image,
+    size: Union[Sequence[int], int],
+    interpolation: int = Image.BILINEAR,
+    max_size: Optional[int] = None,
+) -> Image.Image:
+
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
     if not (isinstance(size, int) or (isinstance(size, Sequence) and len(size) in (1, 2))):
@@ -242,7 +266,12 @@ def resize(img, size, interpolation=Image.BILINEAR, max_size=None):
 
 
 @torch.jit.unused
-def _parse_fill(fill, img, name="fillcolor"):
+def _parse_fill(
+    fill: Optional[Union[float, List[float], Tuple[float, ...]]],
+    img: Image.Image,
+    name: str = "fillcolor",
+) -> Dict[str, Optional[Union[float, List[float], Tuple[float, ...]]]]:
+
     # Process fill color for affine transforms
     num_bands = len(img.getbands())
     if fill is None:
@@ -261,7 +290,13 @@ def _parse_fill(fill, img, name="fillcolor"):
 
 
 @torch.jit.unused
-def affine(img, matrix, interpolation=0, fill=None):
+def affine(
+    img: Image.Image,
+    matrix: List[float],
+    interpolation: int = Image.NEAREST,
+    fill: Optional[Union[float, List[float], Tuple[float, ...]]] = 0,
+) -> Image.Image:
+
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -271,7 +306,15 @@ def affine(img, matrix, interpolation=0, fill=None):
 
 
 @torch.jit.unused
-def rotate(img, angle, interpolation=0, expand=False, center=None, fill=None):
+def rotate(
+    img: Image.Image,
+    angle: float,
+    interpolation: int = Image.NEAREST,
+    expand: bool = False,
+    center: Optional[Tuple[int, int]] = None,
+    fill: Optional[Union[float, List[float], Tuple[float, ...]]] = 0,
+) -> Image.Image:
+
     if not _is_pil_image(img):
         raise TypeError("img should be PIL Image. Got {}".format(type(img)))
 
@@ -280,7 +323,13 @@ def rotate(img, angle, interpolation=0, expand=False, center=None, fill=None):
 
 
 @torch.jit.unused
-def perspective(img, perspective_coeffs, interpolation=Image.BICUBIC, fill=None):
+def perspective(
+    img: Image.Image,
+    perspective_coeffs: float,
+    interpolation: int = Image.BICUBIC,
+    fill: Optional[Union[float, List[float], Tuple[float, ...]]] = 0,
+) -> Image.Image:
+
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -290,7 +339,7 @@ def perspective(img, perspective_coeffs, interpolation=Image.BICUBIC, fill=None)
 
 
 @torch.jit.unused
-def to_grayscale(img, num_output_channels):
+def to_grayscale(img: Image.Image, num_output_channels: int) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -308,28 +357,28 @@ def to_grayscale(img, num_output_channels):
 
 
 @torch.jit.unused
-def invert(img):
+def invert(img: Image.Image) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
     return ImageOps.invert(img)
 
 
 @torch.jit.unused
-def posterize(img, bits):
+def posterize(img: Image.Image, bits: int) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
     return ImageOps.posterize(img, bits)
 
 
 @torch.jit.unused
-def solarize(img, threshold):
+def solarize(img: Image.Image, threshold: int) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
     return ImageOps.solarize(img, threshold)
 
 
 @torch.jit.unused
-def adjust_sharpness(img, sharpness_factor):
+def adjust_sharpness(img: Image.Image, sharpness_factor: float) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
 
@@ -339,14 +388,14 @@ def adjust_sharpness(img, sharpness_factor):
 
 
 @torch.jit.unused
-def autocontrast(img):
+def autocontrast(img: Image.Image) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
     return ImageOps.autocontrast(img)
 
 
 @torch.jit.unused
-def equalize(img):
+def equalize(img: Image.Image) -> Image.Image:
     if not _is_pil_image(img):
         raise TypeError('img should be PIL Image. Got {}'.format(type(img)))
     return ImageOps.equalize(img)