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img_stega.py
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img_stega.py
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import cv2
def str_encode_to_img(s, img):
# 字符串加密并写进图片
X = img.shape[0] # height
Y = img.shape[1] # width
Z = img.shape[2] # depth
img_usable_bit = X*Y*Z*1 # 图片可用于加密的位数
print('Image usable bit number:', img_usable_bit)
s_bytes = s.encode(encoding='utf-8') # 编码字符串
print('String length:', len(s_bytes))
s_bit_length = len(s_bytes)*8 # 字符串位长度=字符串长度x8
print('String bit length:', s_bit_length)
assert s_bit_length <= img_usable_bit-24 # 前24位用于存放字符串长度信息
s_bit_length_bytes = bin(s_bit_length) # 字符串长度二进制编码对应的字符串 0b0001000
s_bit_length_bytes = s_bit_length_bytes.replace('0b', '') # 去除二进制字符串开头的Ob
print('String bit length bytes:', s_bit_length_bytes)
assert len(s_bit_length_bytes) < 24 # 字符串长度整形对应的二进制位数不得超过24 即3个字节
# 写入字符串长度信息
x, y, z = 0, 0, 0
# 从后往前依次填充字符串长度对应的二进制位 到图像前8个像素
for i in range(len(s_bit_length_bytes)-1, -1, -1):
bit = s_bit_length_bytes[i]
channel = img[x][y][z]
channel = channel & 0b11111110 # uint8->int32 最后一位置0
if bit == '1':
channel = channel ^ 0b00000001
elif bit == '0':
channel = channel ^ 0b00000000
img[x][y][z] = channel # 修改原图像像素通道值
if z < Z-1:
z = z+1
else:
z = 0
if y < Y-1:
y = y+1
else:
y = 0
if x < X-1:
x = x+1
# 确保前8个像素点中 除去已经写入文件长度信息外 剩下的每一通道的最后1位全为0
while(y < 8):
channel = img[x][y][z]
channel = channel & 0b11111110 # uint8->int32 最后一位置0
img[x][y][z] = channel
if z < Z-1:
z = z+1
else:
z = 0
y = y+1
x, y, z = 0, 8, 0
for s_byte in s_bytes:
s_byte = bin(s_byte).replace('0b', '')
# 不足8位补全8位 如101000
diff = 8-len(s_byte)
s_byte = '0'*diff+s_byte
for bit in s_byte:
channel = img[x][y][z]
channel = channel & 0b11111110 # uint8->int32 最后一位置0
if bit == '1':
channel = channel ^ 0b00000001
elif bit == '0':
channel = channel ^ 0b00000000
img[x][y][z] = channel # 修改原图像的像素通道值
if z < Z-1:
z += 1
else:
z = 0
if y < Y-1:
y += 1
else:
y = 0
if x < X-1:
x += 1
return img
def str_decode_from_img(img):
# 从加密图片中解密出字符串
X = img.shape[0] # height
Y = img.shape[1] # width
Z = img.shape[2] # depth
x, y, z = 0, 0, 0
n = 0
s = ''
# 解码字符串长度 前8个像素点 8*3=24位
while n < 24:
channel = img[x][y][z]
s += bin(channel)[-1] # 提取最后一位
if z < Z-1:
z += 1
else:
z = 0
if y < Y-1:
y += 1
else:
y = 0
if x < X-1:
x += 1
n += 1
s = s[::-1]
length = int(s, 2)
print('Decoded string bit length:', length)
# 解码字符串
s = ''
n = 0
x, y, z = 0, 8, 0 # 从第一行第8个像素点开始
while n < length/8:
n2 = 0
letter = '' # 每8位组成一个字母
while n2 < 8:
channel = img[x][y][z]
letter += bin(channel)[-1] # 提取最后一位
if z < Z-1:
z += 1
else:
z = 0
if y < Y-1:
y += 1
else:
y = 0
if x < X-1:
x += 1
n2 += 1
n += 1
s += chr(int(letter, 2))
return s
if __name__ == "__main__":
# string you want to encode
s = 'Hello,world!'
print('String unencoded:', s)
# encode string to img
img = cv2.imread('raw.png')
img = str_encode_to_img(s, img)
cv2.imwrite('encoded.png', img)
# decode string from img
img = cv2.imread('encoded.png')
s = str_decode_from_img(img)
print('Decoded string:', s)