- The hidden quote is "Three may keep a secret, if two of them are dead. - Benjamin Franklin".
- A key is on the line
Solution Code:
import cv2 as cv
import numpy as np
WEIGHTS = 1 << np.arange(7, -1, -1)
def get_uint16(bits: np.ndarray) -> int:
uint16_bytes = bits[:16].reshape(-1, 8) @ WEIGHTS
return (uint16_bytes[0] << 8) | uint16_bytes[1]
def decode1(data: np.ndarray) -> str:
bits = data.flatten() & np.uint8(1)
assert bits[0] == bits[1] == 0
length = get_uint16(bits[2:18])
data_bytes = bits[18 : 18 + length].reshape(-1, 8) @ WEIGHTS
return "".join(map(chr, data_bytes))
def decode2(data: np.ndarray) -> np.ndarray:
bits = data.flatten() & np.uint8(1)
assert bits[0] == 1 and bits[1] == 0
width = get_uint16(bits[2:18])
height = get_uint16(bits[18:34])
img_bits = bits[34 : 34 + width * height]
img = (img_bits.reshape(height, width) * 255).astype(np.uint8)
return img
def main() -> None:
img1 = cv.imread("img1.png")
img1 = cv.cvtColor(img1, cv.COLOR_BGR2RGB)
print(decode1(img1))
img2 = cv.imread("img2.png")
img2 = cv.cvtColor(img2, cv.COLOR_BGR2RGB)
img2 = decode2(img2)
cv.imshow("Decoded Image", img2)
cv.waitKey(0)
cv.destroyAllWindows()
if __name__ == "__main__":
main()
Decoded message:
The first part of the sentence is "Three may keep a secret, ...".
### Task 2: Decode a binary image
A binary image is hidden in the least significant bits of the butterfly image, the encoding scheme is:
- Simple LSB Encoding**
- Header: `[1, 0]`
- Next 16 bits: image `width` in pixels
- Next 16 bits: image `height` in pixels
- Raw pixels of the binary image
Hint: Create and fill an image array of the derived `width` and `height` with the encoded hidden pixels.
In order to view your image in classic viewers, it might be helpful to map 0 -> 0 and 1 -> 255.
Derive the second part of the sentence and answer the question about the image
