esp-idf-ssd1306/BdfFontDemo/README.md

BdfFontDemo for SSD1306

u8g2 is a great Library for monochrome displays.
This library contains a lot of BDF format fonts.
This project is a demo that displays BDF format fonts.

How to use BDF Font

• Download the BDF font file.
  Thank you olikraus for releasing useful software.

git clone https://github.com/olikraus/u8g2
ls $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/bdf

• Convert BDF font files to header files.
  I used this repository.
  Thank you Pixelmatix for releasing useful software.

cc -o bdf2c bdf2c.c

./bdf2c -n ncenR12 -b < $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/bdf/ncenR12.bdf > main/ncenR12.h

./bdf2c -n timR12 -b < $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/bdf/timR12.bdf > main/timR12.h

./bdf2c -n battery -b < $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/battery/battery19.bdf > main/battery.h

./bdf2c -n emoticons -b < $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/emoticons/emoticons21.bdf > main/emoticons.h

./bdf2c -n Scroll_o_Sprites -b < $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/pbm/Scroll-o-Sprites.bdf > main/Scroll-o-Sprites.h

• BDF font files can be viewed with the following command.

./bdf2c -B < $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/bdf/ncenR12.bdf | more

./bdf2c -B < $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/bdf/timR12.bdf | more

./bdf2c -B < $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/battery/battery19.bdf | more

./bdf2c -B < $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/emoticons/emoticons21.bdf | more

./bdf2c -B < $HOME/u8g2-hal-esp-idf/examples/i2c/components/u8g2/tools/font/pbm/Scroll-o-Sprites.bdf | more

• Add header files to main.c.

#include "ssd1306.h"
#include "ncenR12.h"
#include "timR12.h"
#include "battery.h"
#include "emoticons.h"
#include "Scroll-o-Sprites.h"

• Show BDF Font

ssd1306_clear_screen(&dev, false);
ssd1306_contrast(&dev, 0xff);
show_bdf_font_text(&dev, __ncenR12_bitmap__, "Hello World", 0, 0);
show_bdf_font_code(&dev, __battery_bitmap__, 48, 100, 0);
show_bdf_font_code(&dev, __battery_bitmap__, 49, 110, 0);
show_bdf_font_code(&dev, __battery_bitmap__, 50, 120, 0);

Font display position

The font's display position starts from the upper left corner of this image.
Therefore, there will be some white space above the font.

________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
XXXXXX_X,XXXXX___,________,
__XX____,_XX_____,________,
__XX____,_XX_____,________,
__XX____,_XX_____,________,
__XX____,_XX_____,________,
__XXXXXX,XXX_____,________,
__XX____,_XX_____,________,
__XX____,_XX_____,________,
__XX____,_XX_____,________,
__XX____,_XX_____,________,
__XX____,_XX_____,________,
XXXXXX_X,XXXXX___,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,

Font bounding box

Fonts are stored as follows.
Each character has a bounding box (BBX).
This BBX value indicates that it should be moved one pixel to the right when displayed.
By providing a bounding box (BBX), this can omit the leftmost blank space.

STARTCHAR d
ENCODING 100
SWIDTH 574 0
DWIDTH 10 0
BBX 8 12 1 0
BITMAP
0E
06
06
06
3E
66
C6
C6
C6
C6
66
3B
ENDCHAR

Fonts that take bounding box (BBX) into consideration change as follows.

STARTCHAR d
ENCODING 100
SWIDTH 574 0
DWIDTH 10 0
BBX 9 12 0 0
BITMAP
07
03
03
03
1F
33
63
63
63
63
33
1D8
ENDCHAR

This image takes into account the bounding box (BBX) of each character.

________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
_____XXX,________,________,
______XX,________,________,
______XX,________,________,
______XX,________,________,
___XXXXX,________,________,
__XX__XX,________,________,
_XX___XX,________,________,
_XX___XX,________,________,
_XX___XX,________,________,
_XX___XX,________,________,
__XX__XX,________,________,
___XXX_X,X_______,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,