Reading or writing secret text from/to uncompressed raster image (PNG, GIF, ...). Every 3 bits are encoded to 3x3 pixelgrid. Central pixel keeps the information, each channel of RGB represents one bit. If at least one of a neighbouring pixels color channel is same as color channel of central pixel, it's a logical one(true), else logical zero(false).

The most beautiful thing is that you almost can't recognize, if image keeps some secret message. It looks like very similar to original.

With this python script you can send image from your vacation with some encoded text to your friend and nobody supposes anything strange.

Script usage

Write these commands in Linux bash terminal:

Write secret text to image

cryptopng image <<< "secret message"

Read text from image

cryptopng image

Print count of chars image can keep

cryptopng --capacity image

Show script usage

cryptopng --help

Feedback

Suggestions and bugs send to smejkalv_AT_gmail_DOT_com.

Thank you.