Myzel394/semi-visible-image-steganography

Example

Given the following image:

it probably looks like an image with a solid fill color.

However, watch what happens when the contrast is increased a lot:

The image is actually a bunch of blobs with different colors.

If we treat the image as a binary image, using 0 for the dark color and 1 for the light color, we get the following content:

0110110101111001011110100110010101101100001100110011100100110100011011010111100101111010011001010110

If we divide this into blocks of 8 bits (= 1 byte) and take the first 8 bytes, we get the following:

01101101 01111001 01111010 01100101 01101100 00110011 00111001 00110100

If we convert this to ASCII, we get the following:

myzel394

This is the text that was used to generate the image.

So basically you can watermark your images by using the text you want to watermark as the fill color!

Usage

Installation

Download the latest release from the releases page or build it yourself.

Command line

$ semi-visible-image-steganography --help
Encode data into an image that can be used as an image background then

Usage: semi-visible-image-steganography [OPTIONS] <text>

Arguments:
  <text>
          Text to encode. Must be ASCII

Options:
  -o, --output <output>
          Output file
          
          [default: output.png]

      --image-width <image-width>
          Width of the image
          
          [default: 1000]

      --image-height <image-height>
          Height of the image
          
          [default: 1000]

  -x, --pixel-width <pixel-width>
          Width of a pixel
          
          [default: 8]

  -y, --pixel-height <pixel-height>
          Height of a pixel
          
          [default: 8]

      --on-color <on-color>
          Color of a pixel when the data is 1
          
          [default: #FFF]

      --off-color <off-color>
          Color of a pixel when the data is 0
          
          [default: #000]

  -l, --fill-color <fill-color>
          Default fill color of the image. Pixels will overwrite this color
          
          [default: #000]

  -r, --remaining-behavior <remaining-behavior>
          What to do with the remaining data
          
          [default: take-firsts]

          Possible values:
          - pad-with-null: Pad with 0s
          - do-nothing:    Do nothing
          - take-firsts:   Take the firsts

  -h, --help
          Print help (see a summary with '-h')

  -V, --version
          Print version

Examples

Generate the example image: semi-visible-image-steganography "myzel394" --on-color "#182249" --off-color "#182242" -l "#182242" --image-width 100 --image-height 100

Experiments

Environment

To test out how well the information is preserved when using JPEG compression, I compressed the images with different on / off colors differences and JPEG qualities.

Here are all commands used:

Generate image: semi-visible-image-steganography --image-width 1920 --image-height 1080 "created by myzel394" --on-color "$1" --off-color "$2" --fill-color "#000"
Compress image: magick image.png -quality $3 out.jpg

$1 = on color $2 = off color

"1 value difference" = there's one number difference between the colors, like: "#030914" and "#030814"
"1 lightness difference" = there's one lightness difference between the colors. I used HSL to add / remove one lightness value, like: "#030916" and "#040B1B"

Results

The following results all used 8x8 blocks.

Using a 1 value difference with quality 90 resulted in preserving the information.
Using a 1 value difference with quality 80 resulted in losing the information.
Using a 1 lightness difference with quality 50 resulted in preserving the information - However, the blobs were clearly visible to me.
Using a 14 value difference with quality 90 and 1x1 blocks resulted in losing the information.
Using a 14 value difference with quality 90 and 10x10 blocks resulted in preserving the information - Plus, the blobs look funny.

Try to use PNG instead of JPEG if you want to preserve the information.

Myzel394 / semi-visible-image-steganography