pic.py

import os   #The OS module in Python provides functions for interacting with the operating system. 
from PIL import Image   #PIL is the python image library which needs to be preinstalled before you can run this code
import random
import feistel

chr_ascii={}        #dictionary containing characters as keys and ascii values as values
ascii_chr={}        #dictionary containing ascii values as keys and characters as values

for i in range(0,256):
    chr_ascii[chr(i)]=i
    ascii_chr[i]=chr(i)
    
def encrypt():
    img=input("\nEnter the name of the image you want the message to be encoded in, with the extension\n\n")

    path=os.path.abspath(img)    #this gives the absolute path of the given file
    image=Image.open(path)
    
    height=image.height
    width=image.width

    password=input("\n\nEnter security key\n\n")

    user=input("\n\nEnter the message you wanna encode\n\n")
    
    #Feistel encryption begins
    message = feistel.text_process(user)
    length = len(message)

    k1 = feistel.key_gen(length, length)
    k2 = feistel.key_gen(length/2, length)

    text = feistel.feistel_encrypt(message, k1, k2) #Encrypted text which will be hidden in image

    #Image steganography from here onwards
    p=0
    j=0
    z=0

    text_length=len(text)
    image.putpixel((0,0),(text_length//255, text_length%255,0))
    random.seed(password)
    x = random.sample(range(1,width+1), text_length)
    y = random.sample(range(1, height+1), text_length)
    coor = list(zip(x,y))

    for i in range(text_length):
        RGB=image.getpixel(coor[i])
        rgb_mutable=list(RGB)
        rgb_mutable[z]=chr_ascii[text[p]]^chr_ascii[password[j]]
        rgb_tuple=tuple(rgb_mutable)
        image.putpixel(coor[i],rgb_tuple)
        
        
        z=(z+1)%3
        j=(j+1)%len(password)
        p+=1

        
    image.show()
    image.save(img[:-4]+"_encrypt.png")


    print("\n\nData hiding in image is successful\n\n")



def decrypt():
    img=input("\nEnter the name of the image you want the message to be decoded from, with the extension\n\n")

    path=os.path.abspath(img)    #this gives the absolute path of the given file

    image=Image.open(path)

    height=image.height
    width=image.width

    j1=0
    
    z1=0
    password=input("\n\nEnter your key\n\n")
    message=''
    raw=list(image.getpixel((0,0)))
    length = raw[0]*255 + raw[1]
    
    random.seed(password)
    x = random.sample(range(1,width+1), length)
    y = random.sample(range(1, height+1), length)
    coor = list(zip(x,y))

    for i in range(length):
        RGB2=image.getpixel(coor[i])
        coded=RGB2[z1]
        
        message+=ascii_chr[coded^chr_ascii[password[j1]]]
        
        z1=(z1+1)%3
        j1=(j1+1)%len(password)

    #Feistel decryption begins
    message = feistel.text_process(message)
    length = len(message)

    k1 = feistel.key_gen(length, length)
    k2 = feistel.key_gen(length/2, length)

    ans = feistel.feistel_decrypt(message, k1, k2)
    print("\n\nEncrypted text was\n\n", ans)   

user = input("Type 'encrypt' if you want encryption \nType 'decrypt' if you want decryption\n" )

if user == 'encrypt':
    encrypt()
elif user == 'decrypt':
    decrypt()
else:
    print("Invalid entry")