erosion_operation.py

frompathlibimportPath

importnumpyasnp
fromPILimportImage


defrgb_to_gray(rgb: np.ndarray) ->np.ndarray:
"""
 Return gray image from rgb image

 >>> rgb_to_gray(np.array([[[127, 255, 0]]]))
 array([[187.6453]])
 >>> rgb_to_gray(np.array([[[0, 0, 0]]]))
 array([[0.]])
 >>> rgb_to_gray(np.array([[[2, 4, 1]]]))
 array([[3.0598]])
 >>> rgb_to_gray(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]
return0.2989*r+0.5870*g+0.1140*b


defgray_to_binary(gray: np.ndarray) ->np.ndarray:
"""
 Return binary image from gray image

 >>> gray_to_binary(np.array([[127, 255, 0]]))
 array([[False, True, False]])
 >>> gray_to_binary(np.array([[0]]))
 array([[False]])
 >>> gray_to_binary(np.array([[26.2409, 4.9315, 1.4729]]))
 array([[False, False, False]])
 >>> gray_to_binary(np.array([[26, 255, 14], [5, 147, 20], [1, 200, 0]]))
 array([[False, True, False],
 [False, True, False],
 [False, True, False]])
 """
return (gray>127) & (gray<=255)


deferosion(image: np.ndarray, kernel: np.ndarray) ->np.ndarray:
"""
 Return eroded image

 >>> erosion(np.array([[True, True, False]]), np.array([[0, 1, 0]]))
 array([[False, False, False]])
 >>> erosion(np.array([[True, False, False]]), np.array([[1, 1, 0]]))
 array([[False, False, False]])
 """
output=np.zeros_like(image)
image_padded=np.zeros(
 (image.shape[0] +kernel.shape[0] -1, image.shape[1] +kernel.shape[1] -1)
 )

# Copy image to padded image
image_padded[kernel.shape[0] -2 : -1 :, kernel.shape[1] -2 : -1 :] =image

# Iterate over image & apply kernel
forxinrange(image.shape[1]):
foryinrange(image.shape[0]):
summation= (
kernel*image_padded[y : y+kernel.shape[0], x : x+kernel.shape[1]]
 ).sum()
output[y, x] =int(summation==5)
returnoutput


if__name__=="__main__":
# read original image
lena_path=Path(__file__).resolve().parent/"image_data"/"lena.jpg"
lena=np.array(Image.open(lena_path))

# kernel to be applied
structuring_element=np.array([[0, 1, 0], [1, 1, 1], [0, 1, 0]])

# Apply erosion operation to a binary image
output=erosion(gray_to_binary(rgb_to_gray(lena)), structuring_element)

# Save the output image
pil_img=Image.fromarray(output).convert("RGB")
pil_img.save("result_erosion.png")