esp-idf-ssd1306/BdfFontDemo/README.md

# BdfFontDemo for SSD1306

![BdfFontDemo-1](https://github.com/user-attachments/assets/df733de1-b5b8-4142-8123-5a8f992246ff)
![BdfFontDemo-2](https://github.com/user-attachments/assets/224d12c4-8ecf-4116-868a-8f11ca480122)
![BdfFontDemo-3](https://github.com/user-attachments/assets/4dbb6f39-ae0f-4ca2-9e55-ba32476b018e)

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](https://github.com/pixelmatix/bdf2c) repository.   
 Thank you Pixelmatix for releasing useful software.   
```
cd esp-idf-ssd1306/BdfFontDemo

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 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/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 "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);
```


# 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.   
```
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
______XX,X_______,________,
_____X__,_X______,________,
____X___,_XX_____,________,
____XX__,_XX_____,________,
____XX__,_XX_____,________,
________,XX______,________,
________,X_______,________,
_______X,________,________,
______X_,__X_____,________,
_____X__,__X_____,________,
____XXXX,XXX_____,________,
____XXXX,XXX_____,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
```

# Font bounding box and character bounding box
BDF font file has a font bounding box (FONTBOUNDINGBOX).   
This FONTBOUNDINGBOX value indicates that all fonts must have a 3-pixel margin to the left and a 6-pixel margin below the font.   
```
FONTBOUNDINGBOX 21 26 -3 -6
```

Each character has a character-specific bounding box (BBX).
This BBX value indicates that there should be a 1 pixel margin to the left of this character.
By providing a character-specific 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 character-specific bounding box (BBX) into consideration change as follows.   
```
STARTCHAR d
ENCODING 100
SWIDTH 574 0
DWIDTH 11 0
BBX 9 12 0 0
BITMAP
07
03
03
03
1F
33
63
63
63
63
33
1D8
ENDCHAR
```

Fonts that take character-specific bounding box (BBX) and font bounding box (FONTBOUNDINGBOX) into consideration change as follows.   
```
STARTCHAR d
ENCODING 100
SWIDTH 574 0
DWIDTH 14 0
BBX 9 12 0 0
BITMAP
00
00
00
00
00
00
00
00
00E0
0060
0060
0060
03E0
0660
0C60
0C60
0C60
0C60
0660
030B
00
00
00
00
00
00
ENDCHAR
```

Both the font bounding box (FONTBOUNDINGBOX) and character-specific bounding box (BBX) determine which pixels are displayed.   
This image takes into account the font bounding box (FONTBOUNDINGBOX) and character-specific bounding box (BBX).   
```
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,XXX_____,________,
________,_XX_____,________,
________,_XX_____,________,
________,_XX_____,________,
______XX,XXX_____,________,
_____XX_,_XX_____,________,
____XX__,_XX_____,________,
____XX__,_XX_____,________,
____XX__,_XX_____,________,
____XX__,_XX_____,________,
_____XX_,_XX_____,________,
______XX,X_XX____,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
________,________,________,
```