Own bitmap fonts?

Morning. Is there a way. to make own custom bitmap fonts for bge?
I am referring to these: http://www.tutorialsforblender3d.com/GameDoc/Text/FontSheet_1.html
I know you can convert a font in to a bitmap font (image). But is there more information on what rules are being used to read each letter from that image layout? Could you in theory just paint a custom font right into that image layout?
Or is preferred way to just make an actual custom font first and then convert it in to a bge font sheet.

I hope my question makes any sense.

You can manipulate the image as it is … just an image. make sure NOT to change the dots at the top border of the image (e.g. do not save as jpg).
Make sure your manipulations remain inside the borders of the letters. This method allows to use colored images too.

Indeed you can can create an own font beforehand. This comes handy if you want to change the size of the letters.

Could you in theory just paint a custom font right into that image layout?

Yes but it must have the same size.
That is why it is better to make a custom font and then convert it in to a bge font.

If you find difficult to create your own font, you can use the program FTBlender, available here (http://www.blendenzo.com/tutFTBlender.html) with instructions.