J'aimerai faire l'inverse de mon programme,je bloque passer de image a matrice

from PIL import Image

class Encryption:

    def __init__(self):
        self.string = ""

    def __call__(self):
        self.string = input("Enter your message (< 400 char) :\n")
        output = self.encrypt()

        return output

    def encrypt(self):
        global matrix
        if len(self.string) > 400:
            print("The message is too long. This must be under 400 characters long.")
            return None
        elif len(self.string) < 400:
            for i in range(400-len(self.string)):
                self.string += " "

        matrix = [
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
            [],
        ]

        index_str = 0
        for row in range(20):
            for col in range(20):
                matrix[row].append(ord(self.string[index_str]))
                index_str += 1
        coef = 100
        
        
        image = Image.new("RGB",(len(matrix[0])*coef,len(matrix)*coef))
        for ligne,col in [(x,y) for x in range(len(matrix)) for y in range(len(matrix[0]))]:
            couleur = matrix[ligne][col]
            couleurs = (couleur//(256*256),(couleur-(couleur//(256*256))*256*256)//256,couleur%256)
            for x,y in [(x,y) for x in range(coef) for y in range(coef)]:
                image.putpixel((col*coef+x, ligne*coef+y), couleurs)
        image.show ()
        image.save('image.png')
        return matrix


class Decryption:

    def __init__(self):
        self.matrix = []

    def __call__(self, matrix):
        self.matrix = matrix
        message = self.decrypt()

        return message

    def decrypt(self):
        message = ""

        for row in range(len(self.matrix)):
            for col in range(len(self.matrix[row])):
                message += chr(self.matrix[row][col])

        return message


encrypt_tool = Encryption()
decrypt_tool = Decryption()

output = encrypt_tool()

for i in output:
    print(i)

transmitted_message = decrypt_tool(output)
print("Le message était : ",transmitted_message)>