Image encryption and decryption using AES algorithm

I'm creating Image encryption and decryption using AES algorithm. All of my code runs well and image is being selected for upload and encryption process runs but following error appears Screenshot attached

here is my code

from __future__ import division, print_function, unicode_literals

import sys
import random
import argparse
import logging
from tkinter import *
from tkinter import filedialog
from tkinter import messagebox
import os
import PIL
from PIL import Image
import math
from Crypto.Cipher import AES
import hashlib
import binascii
import numpy as np


global password 

def load_image(name):
    return Image.open(name)

# ----------------- Functions for encryption ---------------------#
def prepare_message_image(image, size):
    if size != image.size:
        image = image.resize(size, Image.ANTIALIAS)
    return image

def generate_secret(size, secret_image = None):
    width, height = size
    new_secret_image = Image.new(mode = "RGB", size = (width * 2, height * 2))

    for x in range(0, 2 * width, 2):
        for y in range(0, 2 * height, 2):
            color1 = np.random.randint(255)
            color2 = np.random.randint(255)
            color3 = np.random.randint(255)
            new_secret_image.putpixel((x,  y),   (color1,color2,color3))
            new_secret_image.putpixel((x+1,y),   (255-color1,255-color2,255-color3))
            new_secret_image.putpixel((x,  y+1), (255-color1,255-color2,255-color3))
            new_secret_image.putpixel((x+1,y+1), (color1,color2,color3))

    return new_secret_image

def generate_ciphered_image(secret_image, prepared_image):
    width, height = prepared_image.size
    ciphered_image = Image.new(mode = "RGB", size = (width * 2, height * 2))
    for x in range(0, width*2, 2):
        for y in range(0, height*2, 2):
            sec = secret_image.getpixel((x,y))
            msssg = prepared_image.getpixel((int(x/2),int(y/2)))
            color1 = (msssg[0]+sec[0])%256
            color2 = (msssg[1]+sec[1])%256
            color3 = (msssg[2]+sec[2])%256
            ciphered_image.putpixel((x,  y),   (color1,color2,color3))
            ciphered_image.putpixel((x+1,y),   (255-color1,255-color2,255-color3))
            ciphered_image.putpixel((x,  y+1), (255-color1,255-color2,255-color3))
            ciphered_image.putpixel((x+1,y+1), (color1,color2,color3))

    return ciphered_image


def generate_image_back(secret_image, ciphered_image):
    width, height = secret_image.size
    new_image = Image.new(mode = "RGB", size = (int(width / 2), int(height / 2)))
    for x in range(0, width, 2):
        for y in range(0, height, 2):
            sec = secret_image.getpixel((x,y))
            cip = ciphered_image.getpixel((x,y))
            color1 = (cip[0]-sec[0])%256
            color2 = (cip[1]-sec[1])%256
            color3 = (cip[2]-sec[2])%256
            new_image.putpixel((int(x/2),  int(y/2)),   (color1,color2,color3))

    return new_image


#------------------------Encryption -------------------#
def level_one_encrypt(Imagename):
    message_image = load_image(Imagename)
    size = message_image.size
    width, height = size

    secret_image = generate_secret(size)
    secret_image.save("secret.jpeg")

    prepared_image = prepare_message_image(message_image, size)
    ciphered_image = generate_ciphered_image(secret_image, prepared_image)
    ciphered_image.save("2-share_encrypt.jpeg")



# -------------------- Construct Encrypted Image  ----------------#
def construct_enc_image(ciphertext, relength, width, height):
    asciicipher = binascii.hexlify(ciphertext)
    def replace_all(text, dic):
        for i, j in dic.iteritems():
            text = text.replace(i, j)
        return text

    reps = {'a':'1', 'b':'2', 'c':'3', 'd':'4', 'e':'5', 'f':'6', 'g':'7', 'h':'8', 'i':'9', 'j':'10', 'k':'11', 'l':'12', 'm':'13', 'n':'14', 'o':'15', 'p':'16', 'q':'17', 'r':'18', 's':'19', 't':'20', 'u':'21', 'v':'22', 'w':'23', 'x':'24', 'y':'25', 'z':'26'}
    asciiciphertxt = replace_all(asciicipher, reps)

    step = 3
    encimageone=[asciiciphertxt[i:i+step] for i in range(0, len(asciiciphertxt), step)]
    # if the last pixel RGB value is less than 3-digits, add a digit as 1
    if int(encimageone[len(encimageone)-1]) < 100:
        encimageone[len(encimageone)-1] += "1"
    if len(encimageone) % 3 != 0:
        while len(encimageone) % 3 != 0:
            encimageone.append("101")

    pixelArray = []
    for i in range(len(encimageone)//3):
        pixelArray.append((int(encimageone[3*i]),int(encimageone[3*i+1]),int(encimageone[3*i+2])))

    image = Image.new("RGB", (width, height))
    image.putdata(pixelArray)
    return image



#------------------------- Visual-encryption -------------------------#
def encrypt(imagename,password):
    plaintext = list()
    plaintextstr = ""

    im = Image.open(imagename) 
    pix = im.load()

    width = im.size[0]
    height = im.size[1]

    # break up the image into a list, each with pixel values and then append to a string
    for y in range(0,height):
        for x in range(0,width):
            print (pix[x,y]) 
            plaintext.append(pix[x,y])
    print(width)
    print(height)

    # add 100 to each tuple value to make sure each are 3 digits long.  
    for i in range(0,len(plaintext)):
        for j in range(0,3):
            aa = int(plaintext[i][j])+100
            plaintextstr = plaintextstr + str(aa)


    # length save for encrypted image reconstruction
    relength = len(plaintext)

    # append dimensions of image for reconstruction after decryption
    plaintextstr += "h" + str(height) + "h" + "w" + str(width) + "w"

    # make sure that plantextstr length is a multiple of 16 for AES.  if not, append "n". 
    while (len(plaintextstr) % 16 != 0):
        plaintextstr = plaintextstr + "n"

    # encrypt plaintext
    obj = AES.new(password, AES.MODE_CBC, 'This is an IV456')
    ciphertext = obj.encrypt(plaintextstr)

    # write ciphertext to file for analysis
    cipher_name = imagename + ".crypt"
    g = open(cipher_name, 'w')
    g.write(ciphertext)
    construct_enc_image(ciphertext,relength,width,height)
    print("Visual Encryption done.......")
    level_one_encrypt("visual_encrypt.jpeg")
    print("2-Share Encryption done.......")




# ---------------------- decryption ---------------------- #
def decrypt(ciphername,password):

    secret_image = Image.open("secret.jpeg")
    ima = Image.open("2-share_encrypt.jpeg")
    new_image = generate_image_back(secret_image, ima)
    new_image.save("2-share_decrypt.jpeg")
    print("2-share Decryption done....")
    cipher = open(ciphername,'r')
    ciphertext = cipher.read()

    # decrypt ciphertext with password
    obj2 = AES.new(password, AES.MODE_CBC, 'This is an IV456')
    decrypted = obj2.decrypt(ciphertext)

    # parse the decrypted text back into integer string
    decrypted = decrypted.replace("n","")

    # extract dimensions of images
    newwidth = decrypted.split("w")[1]
    newheight = decrypted.split("h")[1]

    # replace height and width with emptyspace in decrypted plaintext
    heightr = "h" + str(newheight) + "h"
    widthr = "w" + str(newwidth) + "w"
    decrypted = decrypted.replace(heightr,"")
    decrypted = decrypted.replace(widthr,"")

    # reconstruct the list of RGB tuples from the decrypted plaintext
    step = 3
    finaltextone=[decrypted[i:i+step] for i in range(0, len(decrypted), step)]
    finaltexttwo=[(int(finaltextone[int(i)])-100,int(finaltextone[int(i+1)])-100,int(finaltextone[int(i+2)])-100) for i in range(0, len(finaltextone), step)]

    # reconstruct image from list of pixel RGB tuples
    newim = Image.new("RGB", (int(newwidth), int(newheight)))
    newim.putdata(finaltexttwo)
    newim.save("visual_decrypt.jpeg")
    print("Visual Decryption done......")



# ---------------------
# GUI stuff starts here
# ---------------------

def pass_alert():
   messagebox.showinfo("Password Alert","Please enter a password.")

def enc_success(imagename):
   messagebox.showinfo("Success","Encrypted Image: " + imagename)

# image encrypt button event
def image_open():
    global file_path_e

    enc_pass = passg.get()
    if enc_pass == "":
        pass_alert()
    else:
        password = hashlib.sha256(enc_pass.encode('utf-8')).hexdigest()
        filename = filedialog.askopenfilename()
        file_path_e = os.path.dirname(filename)
        encrypt(filename,password)

# image decrypt button event
def cipher_open():
    global file_path_d

    dec_pass = passg.get()
    if dec_pass == "":
        pass_alert()
    else:
        password = hashlib.sha256(dec_pass.encode('utf-8')).hexdigest()
        filename = filedialog.askopenfilename()
        file_path_d = os.path.dirname(filename)
        decrypt(filename,password)

class App:
  def __init__(self, master):
    global passg
    title = "Image Encryption"
    author = "Made by Aqsa & Sabooha"
    msgtitle = Message(master, text =title)
    msgtitle.config(font=('helvetica', 17, 'bold'), width=200)
    msgauthor = Message(master, text=author)
    msgauthor.config(font=('helvetica',10), width=200)

    canvas_width = 200
    canvas_height = 50
    w = Canvas(master,
           width=canvas_width,
           height=canvas_height)
    msgtitle.pack()
    msgauthor.pack()
    w.pack()

    passlabel = Label(master, text="Enter Encrypt/Decrypt Password:")
    passlabel.pack()
    passg = Entry(master, show="*", width=20)
    passg.pack()

    self.encrypt = Button(master,
                         text="Encrypt", fg="black",
                         command=image_open, width=25,height=5)
    self.encrypt.pack(side=LEFT)
    self.decrypt = Button(master,
                         text="Decrypt", fg="black",
                         command=cipher_open, width=25,height=5)
    self.decrypt.pack(side=RIGHT)


# ------------------ MAIN -------------#
root = Tk()
root.wm_title("Image Encryption")
app = App(root)
root.mainloop()