Store data of any kind inside PNG images
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README.md

s2png — “stuff to PNG”

Build Status AppVeyor CI build status

This program encodes arbitrary binary data in PNG images that look like noise and decodes it back. It was originally developed by k0wax at http://sourceforge.net/projects/s2png/. This fork fixes a libgd-related problem that caused s2png 0.01 to segfault when compiled on a modern operating system and includes various improvements. It remains data-compatible with the original.

s2png is licensed under the GNU GPL 2.0. See the file LICENSE.

Building and installing

*nix

1. Install the build dependencies. On Debian and Ubuntu run sudo apt install build-essential git libgd2-noxpm-dev pkg-config. On FreeBSD run sudo pkg install git gmake libgd pkgconf.

2. Clone the repository and cd into it.

git clone https://github.com/dbohdan/s2png
cd s2png/

3. Build s2png and run the tests for it with make test or gmake test. s2png is known to build correctly and pass the tests on the following operating systems:

  • Debian 9
  • FreeBSD 11.0-RELEASE
  • OpenSUSE Tumbleweed (2017*)
  • Raspbian 8
  • Ubuntu 12.04
  • Ubuntu 16.04

4. Install with sudo make install. You will be able to uninstall s2png with sudo make uninstall. If CheckInstall supports your OS, you should also be able to create and install an uninstallable package for s2png with sudo checkinstall.

Windows

You can download a Windows executable built from the latest commit from AppVeyor.

To build s2png yourself you will need MSYS2. Install it and start the MSYS2 MINGW32 Shell.

1. Install the build dependencies.

pacman -Syuu diffutils git make mingw-w64-i686-gcc mingw-w64-i686-gd mingw-w64-i686-imagemagick wget

2. Clone the repository and cd into it.

git clone https://github.com/dbohdan/s2png
cd s2png/

3. Get sysexits.h, which is required to build s2png, and modify s2png.c to use it.

wget https://raw.githubusercontent.com/freebsd/freebsd/master/include/sysexits.h
sed -i 's/<sysexits.h>/"sysexits.h"/' s2png.c

4. Build s2png.exe executable with make.

5. Create a new directory. Copy the binary and the DLLs it depends on there.

mkdir build/
cp s2png.exe build/
cp /mingw32/bin/{libbz2-1.dll,libexpat-1.dll,libfontconfig-1.dll,libfreetype-6.dll,libgcc_s_dw2-1.dll,libgd-3.dll,libglib-2.0-0.dll,libgraphite2.dll,libharfbuzz-0.dll,libiconv-2.dll,libintl-8.dll,libjpeg-8.dll,liblzma-5.dll,libpcre-1.dll,libpng16-16.dll,libstdc++-6.dll,libtiff-5.dll,libvpx-1.dll,libwinpthread-1.dll,libXpm-noX4.dll,zlib1.dll} build/

The contents of build/ will run on Windows machines without MSYS2.

Usage

s2png ("stuff to png") version 0.7.2
usage: s2png [-h] [-o filename] [-w width (600) | -s] [-b text]
             [-p password] [-e | -d] file

Store any data in a PNG image.
This version can encode files of up to 16777215 bytes.

  -h            display this message and quit
  -o filename   output the encoded or decoded data to filename
  -w width      set the width of the PNG image output (600 by default)
  -s            make the output image roughly square
  -b text       custom banner text ("" for no banner)
  -p password   encrypt/decrypt the output with password using RC4
                (Warning: do not use this if you want actual secrecy!)
Normally s2png detects which operation to perform by the file type. You can
override this behavior with the following switches:
  -e            force encoding mode
  -d            force decoding mode

Examples

To store foo.mp3 in an image enter the following command:

s2png foo.mp3

A file named foo.mp3.png will be created in the same directory as foo.mp3.

Add the -s switch to ensure the resulting image is square (give or take a pixel) and -b "some text" to change the text of the banner at the bottom.

s2png -s -b hello foo.mp3

To decode decode_me.mp3.png and retrieve the original file decode_me.mp3 run the command

s2png decode_me.mp3.png

You can decode xyz.png to decoded.mp3 with

s2png -o decoded.mp3 xyz.png