An image is essentially an array of pixels. Each pixel can have three colour channels - red, green and blue.
Each channel is represented by an 8-bit value, which provides 256 discrete levels of colour.
Some images also have a fourth channel, called the Alpha channel, which is used for pixel transparency.
We shall restrict ourselves to using only the R, G and B channels.
A black and white image uses the same values for R, G and B channels for each pixel.
From Stegosploit