Add type hints for mmcv/image (#2089)

* Fix typehint

* minor fix

* minor fix

* minor fix
Co-authored-by: zhouzaida <zhouzaida@163.com>

mmcv/image/geometric.py

 # Copyright (c) OpenMMLab. All rights reserved.
 import numbers
 import warnings
-from typing import Optional, Tuple
+from typing import List, Optional, Tuple, Union, no_type_check
 
 import cv2
 import numpy as np
@@ -15,7 +15,10 @@ except ImportError:
     Image = None
 
 
-def _scale_size(size, scale):
+def _scale_size(
+    size: Tuple[int, int],
+    scale: Union[float, int, tuple],
+) -> Tuple[int, int]:
     """Rescale a size by a ratio.
 
     Args:
@@ -72,12 +75,14 @@ if Image is not None:
         }
 
 
-def imresize(img,
-             size,
-             return_scale=False,
-             interpolation='bilinear',
-             out=None,
-             backend=None):
+def imresize(
+    img: np.ndarray,
+    size: Tuple[int, int],
+    return_scale: bool = False,
+    interpolation: str = 'bilinear',
+    out: Optional[np.ndarray] = None,
+    backend: Optional[str] = None
+) -> Union[Tuple[np.ndarray, float, float], np.ndarray]:
     """Resize image to a given size.
 
     Args:
@@ -119,15 +124,18 @@ def imresize(img,
         return resized_img, w_scale, h_scale
 
 
-def imresize_to_multiple(img,
-                         divisor,
-                         size=None,
-                         scale_factor=None,
-                         keep_ratio=False,
-                         return_scale=False,
-                         interpolation='bilinear',
-                         out=None,
-                         backend=None):
+@no_type_check
+def imresize_to_multiple(
+    img: np.ndarray,
+    divisor: Union[int, Tuple[int, int]],
+    size: Union[int, Tuple[int, int], None] = None,
+    scale_factor: Union[float, Tuple[float, float], None] = None,
+    keep_ratio: bool = False,
+    return_scale: bool = False,
+    interpolation: str = 'bilinear',
+    out: Optional[np.ndarray] = None,
+    backend: Optional[str] = None
+) -> Union[Tuple[np.ndarray, float, float], np.ndarray]:
     """Resize image according to a given size or scale factor and then rounds
     up the the resized or rescaled image size to the nearest value that can be
     divided by the divisor.
@@ -183,11 +191,13 @@ def imresize_to_multiple(img,
         return resized_img
 
 
-def imresize_like(img,
-                  dst_img,
-                  return_scale=False,
-                  interpolation='bilinear',
-                  backend=None):
+def imresize_like(
+    img: np.ndarray,
+    dst_img: np.ndarray,
+    return_scale: bool = False,
+    interpolation: str = 'bilinear',
+    backend: Optional[str] = None
+) -> Union[Tuple[np.ndarray, float, float], np.ndarray]:
     """Resize image to the same size of a given image.
 
     Args:
@@ -205,7 +215,9 @@ def imresize_like(img,
     return imresize(img, (w, h), return_scale, interpolation, backend=backend)
 
 
-def rescale_size(old_size, scale, return_scale=False):
+def rescale_size(old_size: tuple,
+                 scale: Union[float, int, tuple],
+                 return_scale: bool = False) -> tuple:
     """Calculate the new size to be rescaled to.
 
     Args:
@@ -242,11 +254,13 @@ def rescale_size(old_size, scale, return_scale=False):
         return new_size
 
 
-def imrescale(img,
-              scale,
-              return_scale=False,
-              interpolation='bilinear',
-              backend=None):
+def imrescale(
+    img: np.ndarray,
+    scale: Union[float, Tuple[int, int]],
+    return_scale: bool = False,
+    interpolation: str = 'bilinear',
+    backend: Optional[str] = None
+) -> Union[np.ndarray, Tuple[np.ndarray, float]]:
     """Resize image while keeping the aspect ratio.
 
     Args:
@@ -273,7 +287,7 @@ def imrescale(img,
         return rescaled_img
 
 
-def imflip(img, direction='horizontal'):
+def imflip(img: np.ndarray, direction: str = 'horizontal') -> np.ndarray:
     """Flip an image horizontally or vertically.
 
     Args:
@@ -293,7 +307,7 @@ def imflip(img, direction='horizontal'):
         return np.flip(img, axis=(0, 1))
 
 
-def imflip_(img, direction='horizontal'):
+def imflip_(img: np.ndarray, direction: str = 'horizontal') -> np.ndarray:
     """Inplace flip an image horizontally or vertically.
 
     Args:
@@ -373,7 +387,7 @@ def imrotate(img: np.ndarray,
     return rotated
 
 
-def bbox_clip(bboxes, img_shape):
+def bbox_clip(bboxes: np.ndarray, img_shape: Tuple[int, int]) -> np.ndarray:
     """Clip bboxes to fit the image shape.
 
     Args:
@@ -391,7 +405,9 @@ def bbox_clip(bboxes, img_shape):
     return clipped_bboxes
 
 
-def bbox_scaling(bboxes, scale, clip_shape=None):
+def bbox_scaling(bboxes: np.ndarray,
+                 scale: float,
+                 clip_shape: Optional[Tuple[int, int]] = None) -> np.ndarray:
     """Scaling bboxes w.r.t the box center.
 
     Args:
@@ -417,7 +433,12 @@ def bbox_scaling(bboxes, scale, clip_shape=None):
         return scaled_bboxes
 
 
-def imcrop(img, bboxes, scale=1.0, pad_fill=None):
+def imcrop(
+    img: np.ndarray,
+    bboxes: np.ndarray,
+    scale: float = 1.0,
+    pad_fill: Union[float, list, None] = None
+) -> Union[np.ndarray, List[np.ndarray]]:
     """Crop image patches.
 
     3 steps: scale the bboxes -> clip bboxes -> crop and pad.
@@ -450,10 +471,12 @@ def imcrop(img, bboxes, scale=1.0, pad_fill=None):
             patch = img[y1:y2 + 1, x1:x2 + 1, ...]
         else:
             _x1, _y1, _x2, _y2 = tuple(scaled_bboxes[i, :])
+            patch_h = _y2 - _y1 + 1
+            patch_w = _x2 - _x1 + 1
             if chn == 1:
-                patch_shape = (_y2 - _y1 + 1, _x2 - _x1 + 1)
+                patch_shape = (patch_h, patch_w)
             else:
-                patch_shape = (_y2 - _y1 + 1, _x2 - _x1 + 1, chn)
+                patch_shape = (patch_h, patch_w, chn)  # type: ignore
             patch = np.array(
                 pad_fill, dtype=img.dtype) * np.ones(
                     patch_shape, dtype=img.dtype)
@@ -471,12 +494,12 @@ def imcrop(img, bboxes, scale=1.0, pad_fill=None):
         return patches
 
 
-def impad(img,
+def impad(img: np.ndarray,
           *,
-          shape=None,
-          padding=None,
-          pad_val=0,
-          padding_mode='constant'):
+          shape: Optional[Tuple[int, int]] = None,
+          padding: Union[int, tuple, None] = None,
+          pad_val: Union[float, List] = 0,
+          padding_mode: str = 'constant') -> np.ndarray:
     """Pad the given image to a certain shape or pad on all sides with
     specified padding mode and padding value.
 
@@ -554,7 +577,9 @@ def impad(img,
     return img
 
 
-def impad_to_multiple(img, divisor, pad_val=0):
+def impad_to_multiple(img: np.ndarray,
+                      divisor: int,
+                      pad_val: Union[float, List] = 0) -> np.ndarray:
     """Pad an image to ensure each edge to be multiple to some number.
 
     Args:
@@ -570,7 +595,9 @@ def impad_to_multiple(img, divisor, pad_val=0):
     return impad(img, shape=(pad_h, pad_w), pad_val=pad_val)
 
 
-def cutout(img, shape, pad_val=0):
+def cutout(img: np.ndarray,
+           shape: Union[int, Tuple[int, int]],
+           pad_val: Union[int, float, tuple] = 0) -> np.ndarray:
     """Randomly cut out a rectangle from the original img.
 
     Args:
@@ -614,7 +641,7 @@ def cutout(img, shape, pad_val=0):
     if img.ndim == 2:
         patch_shape = (y2 - y1, x2 - x1)
     else:
-        patch_shape = (y2 - y1, x2 - x1, channels)
+        patch_shape = (y2 - y1, x2 - x1, channels)  # type: ignore
 
     img_cutout = img.copy()
     patch = np.array(
@@ -625,7 +652,8 @@ def cutout(img, shape, pad_val=0):
     return img_cutout
 
 
-def _get_shear_matrix(magnitude, direction='horizontal'):
+def _get_shear_matrix(magnitude: Union[int, float],
+                      direction: str = 'horizontal') -> np.ndarray:
     """Generate the shear matrix for transformation.
 
     Args:
@@ -643,11 +671,11 @@ def _get_shear_matrix(magnitude, direction='horizontal'):
     return shear_matrix
 
 
-def imshear(img,
-            magnitude,
-            direction='horizontal',
-            border_value=0,
-            interpolation='bilinear'):
+def imshear(img: np.ndarray,
+            magnitude: Union[int, float],
+            direction: str = 'horizontal',
+            border_value: Union[int, Tuple[int, int]] = 0,
+            interpolation: str = 'bilinear') -> np.ndarray:
     """Shear an image.
 
     Args:
@@ -671,7 +699,7 @@ def imshear(img,
     elif img.ndim == 3:
         channels = img.shape[-1]
     if isinstance(border_value, int):
-        border_value = tuple([border_value] * channels)
+        border_value = tuple([border_value] * channels)  # type: ignore
     elif isinstance(border_value, tuple):
         assert len(border_value) == channels, \
             'Expected the num of elements in tuple equals the channels' \
@@ -689,12 +717,13 @@ def imshear(img,
         # greater than 3 (e.g. shearing masks whose channels large
         # than 3) will raise TypeError in `cv2.warpAffine`.
         # Here simply slice the first 3 values in `border_value`.
-        borderValue=border_value[:3],
+        borderValue=border_value[:3],  # type: ignore
         flags=cv2_interp_codes[interpolation])
     return sheared
 
 
-def _get_translate_matrix(offset, direction='horizontal'):
+def _get_translate_matrix(offset: Union[int, float],
+                          direction: str = 'horizontal') -> np.ndarray:
     """Generate the translate matrix.
 
     Args:
@@ -712,11 +741,11 @@ def _get_translate_matrix(offset, direction='horizontal'):
     return translate_matrix
 
 
-def imtranslate(img,
-                offset,
-                direction='horizontal',
-                border_value=0,
-                interpolation='bilinear'):
+def imtranslate(img: np.ndarray,
+                offset: Union[int, float],
+                direction: str = 'horizontal',
+                border_value: Union[int, tuple] = 0,
+                interpolation: str = 'bilinear') -> np.ndarray:
     """Translate an image.
 
     Args:

mmcv/image/io.py

@@ -3,6 +3,7 @@ import io
 import os.path as osp
 import warnings
 from pathlib import Path
+from typing import Optional, Union
 
 import cv2
 import numpy as np
@@ -42,7 +43,7 @@ imread_flags = {
 imread_backend = 'cv2'
 
 
-def use_backend(backend):
+def use_backend(backend: str) -> None:
     """Select a backend for image decoding.
 
     Args:
@@ -68,7 +69,7 @@ def use_backend(backend):
             raise ImportError('`tifffile` is not installed')
 
 
-def _jpegflag(flag='color', channel_order='bgr'):
+def _jpegflag(flag: str = 'color', channel_order: str = 'bgr'):
     channel_order = channel_order.lower()
     if channel_order not in ['rgb', 'bgr']:
         raise ValueError('channel order must be either "rgb" or "bgr"')
@@ -84,7 +85,9 @@ def _jpegflag(flag='color', channel_order='bgr'):
         raise ValueError('flag must be "color" or "grayscale"')
 
 
-def _pillow2array(img, flag='color', channel_order='bgr'):
+def _pillow2array(img,
+                  flag: str = 'color',
+                  channel_order: str = 'bgr') -> np.ndarray:
     """Convert a pillow image to numpy array.
 
     Args:
@@ -139,11 +142,11 @@ def _pillow2array(img, flag='color', channel_order='bgr'):
     return array
 
 
-def imread(img_or_path,
-           flag='color',
-           channel_order='bgr',
-           backend=None,
-           file_client_args=None):
+def imread(img_or_path: Union[np.ndarray, str, Path],
+           flag: str = 'color',
+           channel_order: str = 'bgr',
+           backend: Optional[str] = None,
+           file_client_args: Optional[dict] = None) -> np.ndarray:
     """Read an image.
 
     Note:
@@ -207,7 +210,10 @@ def imread(img_or_path,
                         'a pathlib.Path object')
 
 
-def imfrombytes(content, flag='color', channel_order='bgr', backend=None):
+def imfrombytes(content: bytes,
+                flag: str = 'color',
+                channel_order: str = 'bgr',
+                backend: Optional[str] = None) -> np.ndarray:
     """Read an image from bytes.
 
     Args:
@@ -240,7 +246,8 @@ def imfrombytes(content, flag='color', channel_order='bgr', backend=None):
             f'backend: {backend} is not supported. Supported '
             "backends are 'cv2', 'turbojpeg', 'pillow', 'tifffile'")
     if backend == 'turbojpeg':
-        img = jpeg.decode(content, _jpegflag(flag, channel_order))
+        img = jpeg.decode(  # type: ignore
+            content, _jpegflag(flag, channel_order))
         if img.shape[-1] == 1:
             img = img[:, :, 0]
         return img
@@ -262,11 +269,11 @@ def imfrombytes(content, flag='color', channel_order='bgr', backend=None):
         return img
 
 
-def imwrite(img,
-            file_path,
-            params=None,
-            auto_mkdir=None,
-            file_client_args=None):
+def imwrite(img: np.ndarray,
+            file_path: str,
+            params: Optional[list] = None,
+            auto_mkdir: Optional[bool] = None,
+            file_client_args: Optional[dict] = None) -> bool:
     """Write image to file.
 
     Note:

mmcv/image/misc.py

 # Copyright (c) OpenMMLab. All rights reserved.
+from typing import Optional
+
 import numpy as np
 
 import mmcv
@@ -9,7 +11,10 @@ except ImportError:
     torch = None
 
 
-def tensor2imgs(tensor, mean=None, std=None, to_rgb=True):
+def tensor2imgs(tensor,
+                mean: Optional[tuple] = None,
+                std: Optional[tuple] = None,
+                to_rgb: bool = True) -> list:
     """Convert tensor to 3-channel images or 1-channel gray images.
 
     Args: