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- #!/usr/bin/env python3
- #
- # Copyright(C) 2021 wuyaoping
- #
- # LSB algorithm has a great capacity but fragile.
- import cv2
- import math
- import os.path as osp
- import numpy as np
- # Insert data in the low bit.
- # Lower make picture less loss but lower capacity.
- BITS = 2
- HIGH_BITS = 256 - (1 << BITS)
- LOW_BITS = (1 << BITS) - 1
- BYTES_PER_BYTE = math.ceil(8 / BITS)
- FLAG = '%'
- def insert(path, txt):
- img = cv2.imread(path, cv2.IMREAD_ANYCOLOR)
- # Save origin shape to restore image
- ori_shape = img.shape
- max_bytes = ori_shape[0] * ori_shape[1] // BYTES_PER_BYTE
- # Encode message with length
- txt = '{}{}{}'.format(len(txt), FLAG, txt)
- assert max_bytes >= len(
- txt), "Message overflow the capacity:{}".format(max_bytes)
- data = np.reshape(img, -1)
- for (idx, val) in enumerate(txt):
- encode(data[idx*BYTES_PER_BYTE: (idx+1) * BYTES_PER_BYTE], val)
- img = np.reshape(data, ori_shape)
- filename, _ = osp.splitext(path)
- # png is lossless encode that can restore message correctly
- filename += '_lsb_embeded' + ".png"
- cv2.imwrite(filename, img)
- return filename
- def extract(path):
- img = cv2.imread(path, cv2.IMREAD_ANYCOLOR)
- data = np.reshape(img, -1)
- total = data.shape[0]
- res = ''
- idx = 0
- # Decode message length
- while idx < total // BYTES_PER_BYTE:
- ch = decode(data[idx*BYTES_PER_BYTE: (idx+1)*BYTES_PER_BYTE])
- idx += 1
- if ch == FLAG:
- break
- res += ch
- end = int(res) + idx
- assert end <= total // BYTES_PER_BYTE, "Input image isn't correct."
- res = ''
- while idx < end:
- res += decode(data[idx*BYTES_PER_BYTE: (idx+1)*BYTES_PER_BYTE])
- idx += 1
- return res
- def encode(block, data):
- data = ord(data)
- for idx in range(len(block)):
- block[idx] &= HIGH_BITS
- block[idx] |= (data >> (BITS * idx)) & LOW_BITS
- def decode(block):
- val = 0
- for idx in range(len(block)):
- val |= (block[idx] & LOW_BITS) << (idx * BITS)
- return chr(val)
- if __name__ == '__main__':
- data = 'A collection of simple python mini projects to enhance your Python skills.'
- input_path = "./example.png"
- res_path = insert(input_path, data)
- res = extract(res_path)
- print(res)
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