Hi,
Although in theory you can scale individual characters of text like an image, it is normally more feasible to load the font several times converted to different sizes. If you don't need all characters (e.g. maybe just numbers and maths symbols) you can save some space there too. Or in many cases you can try L2 or L4 format or even L1 which won't take up as much space. You can experiment a bit to see what looks good on the screen.
If you want just a few sizes, then loading each to a different bitmap handle should work well.
For BT81x, we have a beta sample app below which you can refer to for BT81x. See SampleApp folder in this file and in particular within sampleapp go to src -> Application -> Set_10.c -> ExtendedFormatFont() for an example.
BT81x Sample AppsNote that the file is around 200MBytes.
Best Regards, FTDI Community