ipolypad-js

Browser-first subset of the ipolypad spec. Turns an SVG or PNG into a padded polygon hull for CSS shape-outside and HTML/canvas text-wrap engines like pretext-flow.

Small, focused, intentionally a strict subset of the Python reference — see SPEC.md §5.

Install

npm install ipolypad-js

Use

import { ipolypad } from 'ipolypad-js';

// URL / Blob / Uint8Array / SVGElement / HTMLImageElement all accepted.
const result = await ipolypad('/assets/dragon.svg', {
  size: 200,
  pad: 6,
  maxPoints: 32,
});
// {
//   src: '/assets/dragon.svg',
//   raster: { width: 200, height: 200, pad: 6 },
//   max_points: 32,
//   n_points: 18,
//   points: [[0.500000, 0.020000], ...]
// }

const css = await ipolypad(svgElement, { format: 'css', selector: '.figure' });

Options

| Option | Default | Notes | | ----------------- | ------- | ---------------------------------------- | | size | 200 | Raster canvas size (px, square). | | margin | 20 | Transparent gutter for dilation room. | | pad | 6 | Positive dilates; negative erodes. | | maxPoints | 32 | Final vertex cap. | | samplesPerCurve | 4 | Bezier flatten samples. | | hull | true | Apply convex envelope. | | format | 'json' | 'json' or 'css'. | | selector | — | Wrap CSS in a selector block. |

What's deliberately not here

The JS package assumes alpha-bearing input (SVG or PNG with transparency) and uses a fixed alpha > 24 threshold. It does not do colour-distance background detection, auto-contrast, adaptive thresholding, batch processing, or SVG/PNG/HTML output. Those live in the Python package on purpose. See SPEC §5.

Cross-language parity

On the parity surface (PNG-with-alpha or SVG input, identical options), this package produces byte-identical json and css output to the Python implementation. Enforced by fixtures in tests/parity/.

License

Apache-2.0.