u8x8 font modification on the fly, adding fx

[ilovesushi]

first question
using u8x8 due to small memory foot print. need to add underscore upperscores, draw frames around text or text labels , and probably draw fx on top. how can i read a symbol from a (current)font in a tile buffer for futher modding and printing.
second question
were unable to find any relative info how to load 4x6 font into u8x8 and display, anyway i am planing to construct a tile 8x8 from 4x6 font to compress the output, so how to load font and get the tile buffer of it
appreciate

[olikraus]

first question:

There is a function

void u8x8_get_glyph_data(u8x8_t *u8x8, uint8_t encoding, uint8_t *buf, uint8_t tile_offset) 

which will copy the 8x8 tile into the provided buffer. In Arduino, it might look like this:

uint8_t buf[8];
u8x8_get_glyph_data(u8x8.getU8x8(), 'A', buf, 0);
/* modify the tile in buf */
u8x8.drawTile(1, 2, 1 buf);

There is also an Arduino example, which demonstrates how to rotate a 8x8 tile by 90 degree:

u8g2/sys/arduino/u8x8/Rotate90/Rotate90.ino

Lines 362 to 367 in 416abe4

	void u8x8_draw_glyph_90(u8x8_t *u8x8, uint8_t x, uint8_t y, uint8_t encoding)
	{
	static uint8_t buf[8];
	u8x8_get_glyph_data(u8x8, encoding, buf, 0);
	u8x8_DrawTile(u8x8, x, y, 1, rotate90(buf));
	}

The Rotate90.ino example is also available in Arduino IDE of the latest u8g2 release.

second question:
There is no 4x6 font. You need to convert this into 8x8 tiles.

[ilovesushi]

You are the best. Thanks.
Regarding the second question. I scrolled the font page for u8g2 , there are a lot of 4x6,5x7 fonts, seems I am missing something. They can't be loaded directly to u8x8 because they are for u8g2, but if I could I would draw them as tiles so I would be able to draw 3 or 4 glyph in 8,or 16 space

[olikraus]

The font format differs between u8g2 and u8x8, but you can convert a 4x6 font into u8x8 format. However Each char would be 8 pixel wide.

As an alternative you could use u8g2 in page mode. It will only consume a little bit more RAM. Even better, u8g2 fonts are compressed.

[ilovesushi]

how can i convert a 4x6 font into u8x8 format. and load with u8x8 separately. i am perfectly fine with using gliph and tile functions only to cut out smaller letters

[olikraus]

There is some help in the FAQ:

u8g2/doc/faq.txt

Lines 255 to 289 in eba8b1a

	Q: How can I generate my own font?
	A: The font must be available in .bdf file format. Then use bdfconv to generate
	the font data. The font data can be pasted into an existing file of your project.
	There is also a nice Windows Bitmap Font Editor "Fony" (http://hukka.ncn.fi/?fony)
	which can export .bdf files. A copy of Fony 1.4.7 is available here:
	https://github.com/olikraus/u8g2/tree/master/tools/font/fony
	Q: Where do I find bdfconv?
	A: A Windows executable is available here:
	https://github.com/olikraus/u8g2/tree/master/tools/font/bdfconv
	Use the Makefile in this directory to create a Linux binary.
	Q: How to convert .ttf to .bdf?
	A1: With otf2bdf: http://sofia.nmsu.edu/~mleisher/Software/otf2bdf/
	A2: With FontForge: https://learn.adafruit.com/custom-fonts-for-pyportal-circuitpython-display/conversion
	Q: Which commandline options are required for bdfconv?
	A: "bdfconv -f 1 -m '32-255' -n fontname -o myfont.c myfont.bdf"
	"-f 1" generates a u8g2 font.
	"-m '32-255'" selects unicode 32 to 255. On Windows, please use double quotes: -m "32-255"
	"-n fontname": This is the name of the font in C/C++/Ino files.
	"-o myfont.c": The font array will be stored in this file.
	"myfont.bdf": The input file with the font data (bdf format).
	Q: Is there any further help for the commandline options of bdfconv.exe?
	A: There is an online tool which helps you to derive the commandline options:
	https://stncrn.github.io/u8g2-unifont-helper/
	Many thanks to "stncrn" for making this available.
	Q: Are there any video-tutorials for bdfconv?
	A1: This is what I found on youtube: https://www.youtube.com/watch?v=Igkb7ZmO31A
	The above video uses the -M option (instead of -m) to provide a map file with the unicodes.
	A2: There is a video about fony and how to convert fonts from different sources (ttf, png) with bdfconv.exe:
	https://www.youtube.com/watch?v=WIAcy5FXuAA

To produce u8x8 fonts you need to use "-f 2" instead.
The bdf source is here: https://github.com/olikraus/u8g2/blob/master/tools/font/bdf/4x6.bdf