Added dilation tests and type hints

Author: Spnetic-5

digital_image_processing/morphological_operations/dilation_operation.py

@@ -2,25 +2,47 @@
 from PIL import Image
 
 
-def rgb2gray(rgb):
+def rgb2gray(rgb: np.array) -> np.array:
     """
     Return gray image from rgb image
+    >>> rgb2gray(np.array([[[127, 255, 0]]]))
+    array([[187.6453]])
+    >>> rgb2gray(np.array([[[0, 0, 0]]]))
+    array([[0.]])
+    >>> rgb2gray(np.array([[[2,  4,  1]]]))
+    array([[3.0598]])
+    >>> rgb2gray(np.array([[[26,  255,  14], [ 5,  147, 20], [ 1,  200,  0]]]))
+    array([[159.0524,  90.0635, 117.6989]])
     """
     r, g, b = rgb[:, :, 0], rgb[:, :, 1], rgb[:, :, 2]
     gray = 0.2989 * r + 0.5870 * g + 0.1140 * b
     return gray
 
 
-def gray2binary(gray):
+def gray2binary(gray: np.array) -> np.array:
     """
     Return binary image from gray image
+    >>> gray2binary(np.array([[127, 255, 0]]))
+    array([[False,  True, False]])
+    >>> gray2binary(np.array([[0]]))
+    array([[False]])
+    >>> gray2binary(np.array([[26.2409,  4.9315,  1.4729]]))
+    array([[False, False, False]])
+    >>> gray2binary(np.array([[26,  255,  14], [ 5,  147, 20], [ 1,  200,  0]]))
+    array([[False,  True, False],
+           [False,  True, False],
+           [False,  True, False]])
     """
     return (127 < gray) & (gray <= 255)
 
 
-def dilation(image, kernel):
+def dilation(image: np.array, kernel: np.array) -> np.array:
     """
     Return dilated image
+    >>> dilation(np.array([[True, False, True]]), np.array([[0, 1, 0], [1, 1, 1], [0, 1, 0]]))
+    array([[ True,  True,  True]])
+    >>> dilation(np.array([[True, False, False]]), np.array([[0, 1, 0], [1, 1, 1], [0, 1, 0]]))
+    array([[ True,  True, False]])
     """
     output = np.zeros_like(image)
     image_padded = np.zeros(