stong985 / lvgl-ttf-esp32

LVGL + stb-truetype rendering TrueType on ESP32

LittlevGL + stb_truetype PoC

This is a simple PoC for getting LVGL work with stb_truetype to render TrueType fonts on ESP32.

Tips for Asian fonts

Asian fonts are usually huge, up to a few tens of MB. You may need to trim the font file before dumping it to ESP32.

To do so, have a look at fontTools. Install it by pip install fonttools

Then, for example, go to main/resource directory, and run:

pyftsubset wenquanyi.ttf --text-file=font_subset.txt --output-file=wqy.ttf

...where in this case:

• wenquanyi.ttf is a famous Chinese font, Wen Quan Yi, in TrueType format
• font_subset.txt is the font subset I need for this demo project
• wqy.ttf is the trimmed TrueType font

Here's what it will be like:

To-do

1. Rasterize a lot of fonts may be a bit stressful for CPU and RAM. Therefore we probably need a KV database thing to handle font caching. One possible approach is to use ESP-IDF's NVS and prepare a separate NVS partition for fonts. Then store all rendered font bitmap cache to that partition.
2. Some heap allocations in stb_truetype can probably be avoided to prevent heap fragmentation.

License

MIT or Apache-2.0