buchstabensuppe

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at least better than PIL.ImageFont

toy font rendering for low pixelcount high contrast displays, i. e. openlab's flipdot display.

features

• supports text shaping via harfbuzz
• per grapheme cluster font fallback
• grayscale and binary b/w support

building

requirements:

• redo-c
• Optionally make for install script and such
• utf8proc
• harfbuzz
• libschrift == 0.10.1

# run inside nix-shell if you have nix!

# static library
$ redo libbuchstabensuppe.a

# demo binary
$ redo bs-renderflipdot.exe

# tests
$ redo test.exe && ./test.exe

alternatively you can just run nix-build

demo

if you want to play around with the font rendering in binary mode you can use the dry run mode of the supplied ./bs-renderflipdot.exe (or ./result/bin/bs-renderflipdot if you use nix) binary.

Run ./bs-renderflipdot.exe -? for usage instructions and don't forget -n for dry running!

$ ./bs-renderflipdot.exe -f fonts/unifont.ttf -f fonts/unifont_upper.ttf -n "Greetings ❣️" 2>/dev/null
                                                                                            
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flipdot interaction

the picture above shows buchstabensuppe being used to render text onto a simulated flipdot display. take notice especially of the following:

• fallback fonts are supported: the emoji is not found in unifont.ttf, but rendered from unifont_upper.ttf
• correct text shaping is supported (as far as the font supports it): g̈ which consists of two codepoints is rendered as a combined cluster consisting of two glyphs.

bs-renderflipdot.c is a simple example showing how to interact with a flipdot display. mainly it involves:

• rendering a string to a bitmap using bs_render_utf8_string
• making sure that the dimensions of the display and the image match with bs_bitmap_extend
• processing the resulting bitmap using bs_bitmap_map
• rendering the resulting bitmap on the display using bs_flipdot_render.
• dealing with bitmaps too big for the display using bs_scroll_next_view and bs_page_next_view.

you can also play around with its cli: the following command renders “Hello World” black on white using GNU Unifont onto a flipdot display (or simulator) running on localhost:2323. See bs-renderflipdot(1) for more usage details.

./bs-renderflipdot.exe -f /path/to/unifont.ttf -f /path/to/unifont_upper.ttf -i "Hello World"

caveats

• buchstabensuppe loads all fonts into memory and keeps them there pretty much all the time.
• there is no support for right to left nor vertical script (but planned)