Simple Steganography: Store and retrieve text messages hidden in images

This class can store and retrieve text messages hidden in images.

It can read an image in PNG or JPEG format and store hidden text messages in the image by altering the color of some pixels to values that include encoded versions of the message text characters.

The altered image is saved in the PNG format.

The class can also do the opposite, i.e. read an image in PNG format to find and decode a hidden text message previously stored in the image pixels using this class.