python - reconstruct the source file from string output -


i use stepic3 hide data. multiple files compressed zip file, hidden message. however, when use following code

from pil import image import stepic  def enc_():     im = image.open("secret.png")     text = str(open("source.zip", "rb").read())     im = stepic.encode(im, text)     im.save('stegolena.png','png')    def dec_():     im1=image.open('stegolena.png')     out = stepic.decode(im1)     plaintext = open("out.zip", "w")     plaintext.write(out)     plaintext.close()

i error

complete trace traceback (most recent call last):   file "c:\users\sherif\onedrive\pyhton projects\kivy tests\simple.py", line 28, in <module>     enc_()   file "c:\users\sherif\onedrive\pyhton projects\kivy tests\simple.py", line 8, in enc_     im = stepic.encode(im, text)   file "c:\users\sherif\onedrive\pyhton projects\kivy tests\stepic.py", line 89, in encode     encode_inplace(image, data)   file "c:\users\sherif\onedrive\pyhton projects\kivy tests\stepic.py", line 75, in encode_inplace     pixel in encode_imdata(image.getdata(), data):   file "c:\users\sherif\onedrive\pyhton projects\kivy tests\stepic.py", line 58, in encode_imdata     byte = ord(data[i]) typeerror: ord() expected string of length 1, int found

there 2 ways convert string.

text = open("source.zip", "r", encoding='utf-8', errors='ignore').read()

with output

pkn!k\z  sec.txt13 byte 1.10mpkn!k\z  sec.txtpk52

or

text = str(open("source.zip", "rb").read())

with output

b'pk\x03\x04\x14\x00\x00\x00\x00\x00n\x8f!k\\\xac\xdaz\r\x00\x00\x00\r\x00\x00\x00\x07\x00\x00\x00sec.txt13 byte 1.10mpk\x01\x02\x14\x00\x14\x00\x00\x00\x00\x00n\x8f!k\\\xac\xdaz\r\x00\x00\x00\r\x00\x00\x00\x07\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xb6\x81\x00\x00\x00\x00sec.txtpk\x05\x06\x00\x00\x00\x00\x01\x00\x01\x005\x00\x00\x002\x00\x00\x00\x00\x00'

i used second , got same string retrival.

in order reconstruct zip file (output string), use code

plaintext = open("out.zip", "w") plaintext.write(output) plaintext.close()

but written file says corrupted when try open it. when try read written it, either

output = output.encode(encoding='utf_8', errors='strict')

or

output = bytes(output, 'utf_8')

the output 

b"b'pk\\x03\\x04\\x14\\x00\\x00\\x00\\x00\\x00n\\x8f!k\\\\\\xac\\xdaz\\r\\x00\\x00\\x00\\r\\x00\\x00\\x00\\x07\\x00\\x00\\x00sec.txt13 byte 1.10mpk\\x01\\x02\\x14\\x00\\x14\\x00\\x00\\x00\\x00\\x00n\\x8f!k\\\\\\xac\\xdaz\\r\\x00\\x00\\x00\\r\\x00\\x00\\x00\\x07\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\xb6\\x81\\x00\\x00\\x00\\x00sec.txtpk\\x05\\x06\\x00\\x00\\x00\\x00\\x01\\x00\\x01\\x005\\x00\\x00\\x002\\x00\\x00\\x00\\x00\\x00'"

which different source file.

what have reconstruct embedded file faithfully?

when read file in rb mode, you'll byte array. if print it, may string, each individual element integer.

>>> my_bytes = b'hello' >>> my_bytes b'hello' >>> my_bytes[0] 104

this explain error

"c:\users\sherif\onedrive\pyhton projects\kivy tests\stepic.py", line 58, in encode_imdata byte = ord(data[i]) typeerror: ord() expected string of length 1, int found

ord() expects string, have convert bytes strings. unfortunately, str(some_byte_array) doesn't think does. creates literal string representation of byte array, including preceeding "b" , surrounding quotes.

>>> string = str(my_bytes) >>> string[0] 'b' >>> string[1] "'" >>> string[2] 'h'

what want instead convert each byte (integer) string individually. map(chr, some_byte_array) you. have because stepic expects string. when embeds character, ord(data[i]), converts string of length 1 unicode code (integer).

furthermore, can't leave our string map object, because code needs calculate length of whole string before embedding it. therefore, ''.join(map(chr, some_bytearray)) have use our input secret.

for extraction stepic opposite. extracts secret byte byte , turns them strings chr(byte). in order reverse that, need ordinal value of each character individually. map(ord, out) should trick. , since want write our file in binary, further feeding bytearray() take care of everything.

overall, these changes should make code.

def enc_():     im = image.open("secret.png")     text = ''.join(map(chr, open("source.zip", "rb").read()))     im = stepic.encode(im, text)     im.save('stegolena.png','png')  def dec_():     im1=image.open('stegolena.png')     out = stepic.decode(im1)     plaintext = open("out.zip", "wb")     plaintext.write(bytearray(map(ord, out)))     plaintext.close()

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