Outguess leaves a signature in file headers after embedding information

[hoijui]

as mentioned here (in an other fork of outguess): crorvick/outguess#1

(NOTE: I did not try if it happens with this outguess too, but I would assume it does)

Outguess doesn't preserve the image header, and if you do hexdump {image}.jpg | grep CDEF you'll see what I mean

[sandsmark]

This looks bogus, outguess just uses a standard copy of libjpeg with a twoline patch that only touches the coefficients calculation, and more or less the example code for writing the jpeg.

The same "signature" is in the libjpeg sample jpegs, even in libjpeg-turbo:

outguess could be improved by using jpeg_read_coefficients() and jpeg_write_coefficients(), though, then it doesn't need to ship a patched copy of libjpeg, improves performance, doesn't need to recompress etc. and can generate an otherwise identical file

[eribertomota]

@sandsmark it is very good idea. Now OutGuess structure is re-organized (after several commits). Do you have time to implement your idea?