This is a handy utility that goes well with the original fontconvert tool provided by Adafruit for converting TTF fonts to Adafruit_GFX .h format.
Just paste the content of a .h font file, extract the glyphs, and you can edit them one by one by flipping the individual pixels for each glyphs, changing the advance, offset, or modifying the baseline.
You can then process our changes and create the improved file.
This is useful since the fontconvert utility does not always create all the characters correctly (a missing pixel here and there). It works best for small size fonts (< 12pt).
 Chris Marrin — added baseline, advance and offset support.
 thelevelofdetail — fixes for negative xOffsets
 Billy Donahue — fixes for xadvance clipping when using oblique fonts
 Mats Engstrom — fixes to allow generating a range of glyphs
 Christof Arnosti — fixes to allow adding characters, improvements for disabled characters
 Marcel Robitaille — feature to allow the conservation of font preamble
MIT. See licence file.