Lipi · लिपि: Devanagari calligraphy with no training

Lipi writes Hindi, Marathi and Sanskrit in eight hands. Two are pen hands: letters drawn by hand for Lipi, stroke by stroke, and written with a hand-set reed pen (lekhani) or brush (tulika). Six are type hands: the outlines of open Devanagari fonts, joined by HarfBuzz and inked onto paper. Nothing in it was learned.

Try it:

• Web app: https://lipi-devanagari-f797919c0a6d.herokuapp.com/
• In your browser (Pyodide): Space: Vishwasaidev/lipi
• Weights + model card: Vishwasaidev/lipi

Lipi is a sister of Quill, the Latin and kanji calligraphy model. The two are kept apart so each keeps its own licences.

python server.py                  # web page on http://127.0.0.1:8793
python lipi.py "सत्यमेव जयते" --style lekhani --initial --seal ॐ
python lipi.py "महाराष्ट्र माझा" --style tiro
python lipi.py "वक्रतुण्ड महाकाय" --style tulika --animate
python lipi.py --demo
python export_weights.py          # data/devanagari + Hershey futural -> weights.safetensors

Requires numpy, pillow, fonttools and uharfbuzz.

The hands

Style	Kind	Look	Letters from
lekhani	pen	broad reed pen: bold headline and horizontals	drawn by hand for Lipi
tulika	pen	brush that presses in and lifts off	drawn by hand for Lipi
kalam	type	everyday handwriting	Kalam, Indian Type Foundry
tiro	type	book type with Marathi letterforms (अ ल श झ)	Tiro Devanagari Marathi, Tiro Typeworks
rozha	type	heavy, high-contrast poster type	Rozha One, Indian Type Foundry
amita	type	calligraphic thick and thin	Amita, Eduardo Tunni
tillana	type	flowing, slanted hand	Tillana, Indian Type Foundry
jaini	type	old manuscript style	Jaini, EkType

--size is the body height in pixels, headline to baseline, for every hand. Inks: iron, black, sepia, sumi, red, blue, green, gold, vermilion.

Extras:

• --initial draws the first syllable about twice the size in red, hanging from the headline.
• --seal carves ॐ or श्री (one word, headline and all) or up to 4 Latin letters into a red seal stamp.
• --animate writes an animated WebP. It starts on blank paper. Pen hands write stroke by stroke and draw each word's headline last; type hands ink each syllable from left to right.
• --flourish adds a tapered swash under the text.

How it works

Layer	Pen hands	Type hands
letters	hand-drawn centrelines (glyphs.deva.* in weights.safetensors)	font outlines, read with fontTools
shaping	fixed rules in devanagari.py (below)	HarfBuzz: the font's own OpenType rules
smooth / pen	Chaikin corner cutting, then a broad nib or a brush swept along each stroke as convex shapes	none: the outline is the shape
raster	half-plane neurons d - nx*x - ny*y per pixel, min over a shape's edges, max over shapes	nonzero-winding scanline fill, 4 x 4 samples per pixel
ink	ink density times paper texture, over cream paper; red initial and seal on their own ink layers	same

In the browser Space, Pyodide has fontTools but not uharfbuzz, so the same HarfBuzz runs as harfbuzzjs (WebAssembly) and hands its results to the Python.

The hand-drawn letters

The strokes in data/devanagari/strokes.txt were drawn by hand for Lipi, point by point on a grid, in writing order: 34 consonants (including ळ), the vowels अ इ उ ऊ ऋ ए (and from them आ ई ओ औ ऐ ऑ ॲ), the vowel signs, ं ँ ः ् ़, ॐ ऽ । ॥, the digits ०-९ and the shapes क्ष त्र ज्ञ श्र. No open data set of Devanagari pen strokes with a clear licence exists. A system font served only as a visual guide while drawing.

devanagari.py shapes text for the pen hands with fixed rules:

• ि is written before the consonant cluster it follows in the text, and its loop reaches over to that cluster.
• Half forms: a consonant whose bar is its right edge drops the bar before another consonant (स्त, न्य, श्व). क and फ have their own half shapes.
• Stacking: a consonant with no bar (द ट ड ह ...) carries the next one small underneath, the Sanskrit way (द्ध, द्व, द्य, ट्ट, ह्न, ह्म).
• Reph (र्म) is a hook above the end of the syllable; rakar (प्र, क्र) is a tick off the bar, or a caret below a letter with no bar (ट्र).
• Vowel signs and ं ँ ः ् ़ hang off the consonant's bar. ँ becomes ं when a vowel sign already sits above.
• The headline is drawn once per word, after its letters.
• Anything else, such as a stack of three consonants, keeps a visible virama. Latin letters, digits and punctuation use the Hershey futural letters.

Data and licences

Each part keeps its own licence:

• Hand-drawn Devanagari strokes (data/devanagari/strokes.txt, and the glyphs.deva.* tensors in weights.safetensors): drawn for Lipi, released under CC BY 4.0.
• Fonts (fonts/): each under the SIL Open Font License 1.1, with its copyright notice in the OFL.txt beside it. Kalam, Rozha One and Tillana: Indian Type Foundry. Tiro Devanagari Marathi: The Indigo Project Authors (Tiro Typeworks). Amita: Eduardo Tunni (with Modular Infotech and Astigmatic). Jaini: The Jaini Project Authors (EkType). They are unmodified and are not part of weights.safetensors.
• Hershey futural letters: public domain (A. V. Hershey, US National Bureau of Standards, 1967), extracted from the MIT-licensed Hershey-Fonts package.
• Code: CC BY 4.0, the same as the strokes.

Limits

• The type hands' letter shapes are the fonts' designers' work. Lipi only joins, places and inks them. They are not written stroke by stroke, so their animation is an ink reveal, not stroke order.
• The pen hands are one hand, drawn once, in a modern print-like form. Marathi's traditional अ, झ, ल and श are not drawn (the tiro hand has them), nor are Vedic accents. Stacks of three or more consonants fall back to a visible virama in the pen hands. The type hands follow each font's own rules and handle them.
• It's slow on a small CPU for the pen hands: a few seconds per image, because every pen step is rasterised separately. Type hands take under a second.