Structure of Adafruit GFX fonts

I 'm using Adafruit 's GFX library for an OLED display.
I 'm using it's standard font, glcdfont.
I 'decypted' it, I mean I analyzed the way they are constructed and so managed to make my own fonts.
I want to do the same for the rest of the fonts (found in the 'fonts' directory of Adafruit_GFX_Library: FreeMono9pt7b, FreeMono12pt7b, FreeMono18pt7b) but they seem to have very strange structure.

For example in glcdfont a character is built of 5 bytes.
Each of these bytes is a column (not a row).

Where can I find this kind of information so that I can modify these fonts and make custom characters?
(or if there is some program that can do this)

And Google is down where you are ? Well i asked my wife She knows everything !

Thank you VERY MUCH!!
I did search a lot but I found nothing, so I was thinking of making my own program!
You saved me!