s2png — “stuff to PNG”

This program encodes arbitrary binary data in PNG images that look like noise and decodes it back. It was originally developed by k0wax on SourceForge. I started this fork to fix a problem that caused s2png 0.01 to segfault when compiled on a modern operating system. The fork has since accumulated various bug fixes and improvements. Most recently, I have ported it to Rust. Among other things, this makes it easier to distribute s2png as a static binary. The fork remains data-compatible with the original if you don't use the toy encryption feature.

Installation

Prebuilt binaries are available for x86_64 Linux and i686 Windows. They are attached to releases on the Releases page. Development (unstable) binaries are also automatically built for Windows.

Installing with Cargo

cargo install s2png

Building on Debian and Ubuntu

Follow the instructions to build a static Linux binary of s2png from source on recent Debian and Ubuntu.

1. Install Rustup. Through Rustup add the stable MUSL target for your CPU.

rustup target add x86_64-unknown-linux-musl

2. Install the build dependencies.

sudo apt install build-essential musl-tools

3. Clone this repository. Build the binary.

git clone https://github.com/dbohdan/s2png
cd s2png
make test
make release-linux

Cross-compiling for Windows

Follow the instructions to build a 32-bit Intel Windows binary of s2png on recent Debian and Ubuntu.

1. Install Rustup. Through Rustup add the i686 GNU ABI Windows target.

rustup target add i686-pc-windows-gnu

2. Install the build dependencies.

sudo apt install build-essential mingw-w64

3. Configure Cargo for cross-compilation. Put the following in ~/.cargo/config.

[target.i686-pc-windows-gnu]
linker = "/usr/bin/i686-w64-mingw32-gcc"

4. Clone this repository. Build the binary.

git clone https://github.com/dbohdan/s2png
cd s2png
make release-windows

Usage

s2png ("stuff to png") version 0.11.1
usage: s2png [-h] [-o filename] [-w width (600) | -s] [-b text]
             [-p hex-key] [-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 hex-key    encrypt/decrypt the output with a hexadecimal key
                using RC4 (Warning: completely insecure! 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

See README.md for further details.

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

Decode xyz.png to decoded.mp3 with

s2png -o decoded.mp3 xyz.png

License

s2png is licensed under the GNU GPL 2.0. See the file LICENSE. The implementation of the RC4 streaming cypher in src/rc4/mod.rs is in the public domain. The font from libgd is distributed under its BSD-like license. See the file src/font/COPYING.libgd.