# jitter
Add natural handwriting-like variation to digital text.
## Why
Digital fonts produce identical glyphs every time the same character appears. Real handwriting never does — each letter has subtle differences in size, angle, position, and weight. jitter brings that organic variation back to digital text.
## Modes
### render
Takes text and a font file, applies per-character random transformations (rotation, anisotropic scale, shear, position drift, subtle stroke-weight variation, and per-point shake), and outputs an SVG or PNG (auto-detected from the `--output` extension).
```
jitter render "Hello, world!" --font my-font.ttf --output hello.svg
jitter render "Hello, world!" --font my-font.ttf --output hello.png
jitter render "手書き風" --font noto-sans-jp.otf --output tegaki.svg --intensity 0.8 --size 64
jitter render "reproducible" --font my-font.ttf --seed 42
```
### bake
Takes a TTF or OTF font and generates N variant glyphs per character, embedding them as an OpenType `calt` feature (contextual alternates). Text rendered with the output font in renderers that honor `calt` can cycle through alternates for consecutive identical glyphs, which makes browser and app support broader than `rand`-only GSUB.
```
jitter bake my-font.ttf --alternates 4 --intensity 0.6
jitter bake my-font.otf --output my-font-jittered.ttf
```
**Bake mode details**:
- Input: TTF or OTF/CFF
- Output: Always TTF (glyf format)
- OTF/CFF inputs are converted to quadratic outlines to fit the TTF glyf table
- GSUB uses `calt`, not `rand`, so repeated identical glyphs can rotate through alternates in browsers too
## Installation
```
cargo install jitter
```
## Usage
```
jitter render <TEXT> --font <FONT> [--output <FILE>] [--intensity <0.0-1.0>] [--size <PX>] [--seed <N>]
jitter bake <INPUT> [--output <FILE>] [--alternates <N>] [--intensity <0.0-1.0>]
```
### Options
- `--font`, `-f`: Path to a .ttf or .otf font file
- `--output`, `-o`: Output file path (default: `output.svg`). Format is auto-detected from the extension (`.svg` or `.png`, render mode only).
- `--intensity`, `-i`: How much variation to apply, from 0.0 (none) to 1.0 (maximum)
- `--size`, `-s`: Font size in pixels (render mode only, default: 48)
- `--seed`: Random seed (u64) for reproducible output. When omitted, output is non-deterministic (render mode only)
- `--alternates`, `-a`: Number of variant glyphs per character (bake mode only, default: 3)
## Output formats
- **SVG**: Vector output, scalable, editable.
- **PNG**: Rasterized output with transparent background (8-bit RGBA). Chosen automatically when the `--output` path ends in `.png`.
## Roadmap
1. ~~render mode (text + font -> SVG with per-character variation)~~ ✓
2. ~~stroke-weight variation for render mode~~ ✓
3. ~~bake mode phase A (TTF + `rand` feature)~~ ✓
4. ~~bake mode phase B (calt-based fallback for wider renderer support)~~ ✓
5. ~~bake mode phase C (OTF/CFF support)~~ ✓
6. line-ending extension / pen-lift exaggeration (future)
7. my-font-craft integration (use jitter as a post-processing step)
## License
MIT