各位高手您好，小妹在試著依據文章打出一樣的程式碼，但總有些問題存在，因此上網請教各位。
文章原文：
An RGB colour image steganography scheme using overlapping block-based pixel-value differencing
以下是我依照學者文章打的程式，但無法呈現相同的結果，另一個問題是裡面有寫到< Threshold，但不曉得Threshold=？

import random
import cv2
import numpy as np
import math


# 藏密
def hide_ori(color_a, color_b):
    a_array = []
    b_array = []
    msg_array = []
    scr=0
    for p1 in range(0, 512, 1):  
        for p2 in range(0, 512, 1):
            dev = color_b[p1,p2] - color_a[p1,p2]
            absdev = abs(dev)
            for i in range(0, 6, 1):  
                if absdev >= lb[i] and absdev <= ub[i]:
                    n = ub[i]-lb[i]+1
                    t = math.log2(n)
                    scr = scr + t
                    msg = random.randint(0, (2**t)-1)
                    msg_array.append(msg)
                    
                    if dev >= 0:
                        dev_new = msg + lb[i]
                    else:
                        dev_new = -(msg + lb[i])
                else:
                    dev_new = dev
            if dev % 2 == 0:
                x = color_a[p1,p2] - math.floor((dev_new-dev)/2)
                y = color_b[p1,p2] + math.ceil((dev_new-dev)/2)                
            else:
                x = color_a[p1,p2] - math.ceil((dev_new-dev)/2)
                y = color_b[p1,p2] + math.floor((dev_new-dev)/2)
            a_array.append(x)
            b_array.append(y)
    return a_array, b_array, scr, msg_array


# 調整數據
def stego(ori_r, ori_g1, ori_g2, ori_b):
    b_array = [] 
    g_array = [] 
    r_array = [] 
    for i in range(0, 262144, 1):
        g = math.ceil((ori_g1[i] + ori_g2[i])/2)
        r = ori_r[i] - (ori_g1[i] - g)
        b = ori_b[i] - (ori_g2[i] - g)
        
        b_array.append(b)
        g_array.append(g)
        r_array.append(r)
    stego_r = np.array(r_array, dtype=np.uint8).reshape(width_ori, height_ori)
    stego_g = np.array(g_array, dtype=np.uint8).reshape(width_ori, height_ori)
    stego_b = np.array(b_array, dtype=np.uint8).reshape(width_ori, height_ori)
    return  stego_r, stego_g, stego_b


# 轉成串列
def turn_list(color):
    cover = np.array(color, dtype=np.int16)  
    cover = [0][0] + cover
    return cover


# MSE
def mse(stego, cover):
    psnrcount = 0
    for i in range(0, width_ori):
        for j in range(0, height_ori):
            psnrtmp = (stego[i][j] - cover[i][j])**2
            psnrcount = psnrcount + psnrtmp
    mse = ((1 / (width_ori * height_ori)) * psnrcount)  
    return mse


# PSNR
def psnr(mse):
    psnr = 10 * (math.log10((255 ** 2) * 3 / mse))
    return psnr

           
if __name__ == '__main__':
    cover = cv2.imread('Figure_7(c).tif')
    width_ori, height_ori, c = cover.shape
    # lowerbound & upperbound
    lb = [0, 8, 16, 32, 64, 128]
    ub = [7, 15, 31, 63, 127, 255]
    cover_b = cover[:,:,0] # B Layer
    cover_g = cover[:,:,1] # G Layer
    cover_r = cover[:,:,2] # R Layer
    cover_b = turn_list(cover_b)
    cover_g = turn_list(cover_g)
    cover_r = turn_list(cover_r)
    r_array, g1_array, scr1, msg1_array = hide_ori(cover_r, cover_g)
    g2_array, b_array, scr2, msg2_array = hide_ori(cover_g, cover_b)
    stego_r, stego_g, stego_b = stego(r_array, g1_array, g2_array, b_array)
    stego = cv2.merge([stego_b, stego_g, stego_r]) #組合影像
    mse_b = mse(stego_b, cover_b)
    mse_g = mse(stego_g, cover_g)
    mse_r = mse(stego_r, cover_r)
    psnr = psnr(mse_b + mse_g + mse_r)
    
    scr = scr1 + scr2
    print(scr)
    print('PSNR=', psnr)

這是文章內學者寫的步驟：
1.Read a RGB pixel from color cover image and decompose it into R, G and B
respectively.
2.Form two pairs like (R, G) and (G, B)
3.Compute t1 = |R − G| and t2 = |G − B|
4.If (t1 + t2) < Threshold Execute Step 5 to 7
5.Apply pixel value differencing (PVD) in both (R,G) and (G,B) pairs to
embed the secret message bits.
6.Get intermediate stego color components
a. R1 and G1 from (R, G) pair
b. G2 and B1 from (G, B) pair
7.Perform readjustment process to form red, green and blue color stego
components based on the following sub steps:
a. Compute GAverage = Round((G1+G2)/2)
b. Modify R1 as final stego red color component
RS = R1 − (G1 − GAverage)
c. Compute final stego green color component
GS = GAverage
d. Modify B1 as final stego blue color component
BS = B1 − (G2 − GAverage)
8.Process rest of the color pixels using step 1 to 7
End.

以下為我的程式結果：
filename=Airplane.tiff, scr=1753707.0, psnr=35.85609494677426
filename=Baboon.tiff, scr=2219652.0, psnr=18.82100840073994
filename=Boat.tiff, scr=2130592.0, psnr=33.33700004304823
filename=house.tiff, scr=2079088.0, psnr=32.20058381417825
filename=lena.tif, scr=2502533.0, psnr=32.29056292944924
filename=Peppers.tiff, scr=2566561.0, psnr=18.278533844395454
學者的文章結果：
filename=Airplane.tiff, scr=1753707.0, psnr=35.66
filename=Baboon.tiff, scr=2219715.0, psnr=32.29
filename=Boat.tiff, scr=2130772.0, psnr=33.11
filename=house.tiff, scr=2079088.0, psnr=34.59
filename=lena.tif, scr= 1976671.0, psnr=31.01
filename=Peppers.tiff, scr=1783210.0, psnr=30.10

真的不曉得問題出在哪裡了，請求大神幫忙