The software can generate any size (in pixel) font. The original screen (ILI9431) was limited to 23bits/pixels height font.
Due to the initial ILI9341 font coding, all fonts reaching a multiple of 8 pixels height (8 bits) are upsized of 8 bits.
- a 7 pixels height font is encoded inside a byte (8 bits) per column.
- a 8 pixels height font will be encoded on 16 bits per column (upsizing).
- Fonts from 9 to 15 pixels height are encoded with 16 bits per column.
- Fonts from 16 to 23 pixels hight are encoded with 24 bits per column.
When generating the values, the numeric values are masked with 0b1111111111 (mask having font_height_in_pixels+1 bits length).
Here is the format of the bin file.
- Magic key - 3 bytes - !FD (0x21, 0x46, 0x44)
- Version - 1 byte - current is 0x01
- Width - 1 byte - NON PROPORTIONNEL font width (so max width) in pixels up to 0xFF
- Height - 1 byte - font height in pixels up to 0xFF
- DataSize - 1 byte - number of bytes per data entry (1,2,3 bytes so 8,16,24 pixels)
- Entries - 1 byte - number of entries in the data section
The data section contains records of data.
Each record entry is composed as following:
- Char Code - 1 byte - ASCII code of the data
- Length - 1 bytes nombre of data of bytes enclosed within the entry
- DATA - * bytes containing the pixels of the character.