# path-intersection

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Computes the intersection between two SVG paths.


## Examples

<img width="600" src="https://raw.githubusercontent.com/bpmn-io/path-intersection/master/resources/examples.png" alt="Intersection examples" />

Execute `npm run dev` and navigate to [`http://localhost:9876/debug.html`](http://localhost:9876/debug.html) to see more examples.


## Usage

```javascript
import intersect from 'path-intersection';

const path0 = 'M30,100L270,20';
const path1 = 'M150,150m0,-18a18,18,0,1,1,0,36a18,18,0,1,1,0,-36z';

const intersection = intersect(path0, path1);
// [ { x: ..., y: ..., segment1: ..., segment2: ... }, ... ]
```

Results are approximate, as we use [bezier clipping](https://math.stackexchange.com/questions/118937) to find intersections.


## Path Caching

Where performance matters, you can pre-parse paths and cache them:

```javascript
import intersect, { parsePath } from 'path-intersection';

// parse paths once
const path1 = parsePath('M0,0L100,100');
const path2 = parsePath('M0,100L100,0');

// they won't be re-parsed during intersection checking
const result1 = intersect(path1, path2);
const result2 = intersect(path2, path2);
```

For repeated calculations, this optimization can result in substantial performance improvements.


## Building the Project

```
# install dependencies
npm install

# build and test the library
npm run all
```


## Credits

The intersection logic provided by this library is derived from [`path.js`](https://github.com/adobe-webplatform/Snap.svg/blob/master/src/path.js), a part of [Snap.svg](https://github.com/adobe-webplatform/Snap.svg).


## License

Use under the terms of the [MIT license](http://opensource.org/licenses/MIT).