pngtext 0.0.9

pngtext

A steganography tool to store text or other data inside PNG images.

Getting Started

Follow these instructions to build pngtext

Prerequisites

You need to have these installed on you machine to build pngtext:

1. dub package manager
   
2. a dlang compiler. dmd works
   
3. an internet connection for dub to fetch the dependencies
   
4. git to clone the repository
   

Building

Run these commands to build pngtext:

git clone https://github.com/Nafees10/pngtext
cd pngtext
dub build --build=release

If the build is succesful, the built binary will be in the current directory named pngtext. Copy the binary to a path where the shell can find it (could be /usr/local/bin).

Running Tests

To run the unittests on pngtext, first cd into the directory containing pngtext, and run: dub test

Using

This describes how to use pngtext.

Writing Data to PNG Image

Use the write command to write data or text to a png image: pngtext write -i pngFile.png -o outputPngFile.png [other options] To write small amount of plain text, use the --text or -t option: pngtext write -i pngFile.png -o outputPngFile.png -t "text to write" To write non-plain-text data, or large amount of text, from file, use the --file or -f option: pngtext write -i pngFile.png -o outputPngFile.png -f fileContainingData

Reading Data from PNG Image:

To read data, that was written using pngtext, use the read command: pngtext read -i pngFile.png To read the stored data into a file, use the --output or -o option to specify the output file: pngtext read -i pngFile.png -o outputDataFile

Calculating Maximum Data Capacity from PNG Image:

To calculate exactly how many bytes a png image will be able to store, use the size command: pngtext size -i pngFile.png This will write the number of bytes a png image can store to stdout.

Specifying How Much Data to Store in Each Pixel

pngtext allows you to specify how many bits are used from each pixel. Each pixel has 4 bytes, and from each of those bytes, a specific number of bits will be used to store the data. This number of bits is referred to as "density" in pngtext. The higher it is, the lower image quality will get, but capacity will increase. It can either be 1, 2, 4, or 8, and the default is 1.

To specify how many bits are to be used, use the --density or -d option: pngtext write -i i.png -o o.png -t someText -d 4 pngtext read -i o.png -d 4 pngtext size -i i.png -d 4 One thing to keep in mind regarding -d option is that if pngtext write if used with -d 4, then pngtext read must also be used with the same number.