steganography.py

import cv2.cv as cv
import sys

class SteganographyException(Exception):
    pass

class LSBSteg():
    def __init__(self, im):
        self.image = im
        self.width = im.width
        self.height = im.height
        self.size = self.width * self.height
        self.nbchannels = im.channels
        
        self.maskONEValues = [1,2,4,8,16,32,64,128]
        #Mask used to put one ex:1->00000001, 2->00000010 .. associated with OR bitwise
        self.maskONE = self.maskONEValues.pop(0) #Will be used to do bitwise operations
        
        self.maskZEROValues = [254,253,251,247,239,223,191,127]
        #Mak used to put zero ex:254->11111110, 253->11111101 .. associated with AND bitwise
        self.maskZERO = self.maskZEROValues.pop(0)
        
        self.curwidth = 0 #Current width position
        self.curheight = 0 #Current height position
        self.curchan = 0 #Current channel position
     
    def saveImage(self,filename):
    # Save the image using the given filename
        cv.SaveImage(filename, self.image)
                    

    def putBinaryValue(self, bits): #Put the bits in the image
        for c in bits:
            val = list(self.image[self.curwidth,self.curheight]) #Get the pixel value as a list
            if int(c) == 1:
                val[self.curchan] = int(val[self.curchan]) | self.maskONE #OR with maskONE
            else:
                val[self.curchan] = int(val[self.curchan]) & self.maskZERO #AND with maskZERO
                
            self.image[self.curwidth,self.curheight] = tuple(val)
            self.nextSpace() #Move "cursor" to the next space
        
    def nextSpace(self):#Move to the next slot were information can be taken or put
        if self.curchan == self.nbchannels-1: #Next Space is the following channel
            self.curchan = 0
            if self.curwidth == self.width-1: #Or the first channel of the next pixel of the same line
                self.curwidth = 0
                if self.curheight == self.height-1:#Or the first channel of the first pixel of the next line
                    self.curheight = 0
                    if self.maskONE == 128: #Mask 1000000, so the last mask
                        raise SteganographyException, "Image filled"
                    else: #Or instead of using the first bit start using the second and so on..
                        self.maskONE = self.maskONEValues.pop(0)
                        self.maskZERO = self.maskZEROValues.pop(0)
                else:
                    self.curheight +=1
            else:
                self.curwidth +=1
        else:
            self.curchan +=1

    def readBit(self): #Read a single bit int the image
        val = self.image[self.curwidth,self.curheight][self.curchan]
        val = int(val) & self.maskONE
        self.nextSpace()
        if val > 0:
            return "1"
        else:
            return "0"
    
    def readByte(self):
        return self.readBits(8)
    
    def readBits(self, nb): #Read the given number of bits
        bits = ""
        for i in range(nb):
            bits += self.readBit()
        return bits

    def byteValue(self, val):
        return self.binValue(val, 8)
        
    def binValue(self, val, bitsize): #Return the binary value of an int as a byte
        binval = bin(val)[2:]
        if len(binval) > bitsize:
            raise SteganographyException, "binary value larger than the expected size"
        while len(binval) < bitsize:
            binval = "0"+binval
        return binval

    def hideText(self, txt):
        l = len(txt)
        binl = self.binValue(l, 16) #Length coded on 2 bytes so the text size can be up to 65536 bytes long
        self.putBinaryValue(binl) #Put text length coded on 4 bytes
        for char in txt: #And put all the chars
            c = ord(char)
            self.putBinaryValue(self.byteValue(c))
       
    def unhideText(self):
        ls = self.readBits(16) #Read the text size in bytes
        l = int(ls,2)
        i = 0
        unhideTxt = ""
        while i < l: #Read all bytes of the text
            tmp = self.readByte() #So one byte
            i += 1
            unhideTxt += chr(int(tmp,2)) #Every chars concatenated to str
        return unhideTxt

    def hideImage(self, imtohide):
        w = imtohide.width
        h = imtohide.height
        if self.width*self.height*self.nbchannels < w*h*imtohide.channels:
            raise SteganographyException, "Carrier image not big enough to hold all the datas to steganography" 
        binw = self.binValue(w, 16) #Width coded on to byte so width up to 65536
        binh = self.binValue(h, 16)
        self.putBinaryValue(binw) #Put width
        self.putBinaryValue(binh) #Put height
        for h in range(imtohide.height): #Iterate the hole image to put every pixel values
            for w in range(imtohide.width):
                for chan in range(imtohide.channels):
                    val = imtohide[h,w][chan]
                    self.putBinaryValue(self.byteValue(int(val)))

                    
    def unhideImage(self):
        width = int(self.readBits(16),2) #Read 16bits and convert it in int
        height = int(self.readBits(16),2)
        unhideimg = cv.CreateImage((width,height), 8, 3) #Create an image in which we will put all the pixels read
        for h in range(height):
            for w in range(width):
                for chan in range(unhideimg.channels):
                    val = list(unhideimg[h,w])
                    val[chan] = int(self.readByte(),2) #Read the value
                    unhideimg[h,w] = tuple(val)
        return unhideimg
    
    def hideBin(self, filename):
        f = open(filename,'rb')
        bin = f.read()
        l = len(bin)
        if self.width*self.height*self.nbchannels < l+64:
            raise SteganographyException, "Carrier image not big enough to hold all the datas to steganography"
        self.putBinaryValue(self.binValue(l, 64))
        for byte in bin:
            self.putBinaryValue(self.byteValue(ord(byte)))
    
    def unhideBin(self):
        l = int(self.readBits(64),2)
        output = ""
        for i in range(l):
            output += chr(int(self.readByte(),2))
        return output
    
if __name__=="__main__":
    pass