In the section “Method 2” of the article https://www.hackthis.co.uk/articles/steganography-how-to-hide-data-inside-image, I don’t understand what the second table stands for.
We have three pixels, [y,x] for y=0, and x=0,1,2 are the coordinates of the three pixels.
The first pixel, [y,x]=[0,0] is associated to 6 bytes denoted by oRv, oGv, …
Just guessing: oXv and nXv stand for original X value and new X value where X may be Red, Green, Blue. [y,x] are simply the pixel coordinates, i.e. y and x value.