Pixel manipulation

from PIL import Image 

#trying the encryption function 
def encrypt_image(image):
    #converting the image to RGB mode 
    image=image.convert('RGB')
    #getting the pixel data
    pixels=image.load()
    
    #encrypting the image by adding a constant value to each pixel
    for x in range(image.width):
        for y in range(image.height):
            r,g,b=pixels[x,y]
            #adding 100 to each pixel value
            pixels[x,y]=((r+100)%256, (g+100)%256, (b+100)%256)
            
    return image

#trying the decryption function 
def decrypt_image(image):
    #converting the image to RGB mode 
    image=image.convert('RGB')
    #getting the pixel data
    pixels=image.load()
    
    #decrypting the image by subtracting same constant value from each pixel
    for x in range(image.width):
        for y in range(image.height):
            r, g, b = pixels[x, y]
            #subtracting 100 from each pixel
            pixels[x, y] = ((r-100)%256, (g-50)%256, (b-50)%256)  
            
    return image 

user_choice=input("Would you like to encrypt or decrypt the image? Type 'encrypt' or 'decrypt': ").lower()
input_image_path = 'input.png'  # Assuming the input image is named input.png
input_image = Image.open(input_image_path)

if user_choice=='encrypt':
    output_image_path='encrypted_image.png'
    output_image = encrypt_image(input_image)
    action = 'encrypted'
elif user_choice == 'decrypt':
    output_image_path = 'decrypted_image.png'
    output_image = decrypt_image(input_image)
    action = 'decrypted'
else:
    print("Invalid choice. Please choose 'encrypt' or 'decrypt'.")
    exit()
    
#saving the output image 
output_image.save(output_image_path)
print(f"The image has been {action}! You can find it saved as '{output_image_path}'.")