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# Rotate feature interaction for OpenLayers

Plugin adds interaction that allows rotating vector features around some anchor.

### [Demo](https://ghettovoice.github.io/ol-rotate-feature/demo.html)

## Installation

Install it with NPM (**recommended**):

```shell
# ES6 version for bundling with Webpack, Rollup or etc.
npm install ol ol-rotate-feature
```

Or add from CDN:

```html
<script src="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v6.0.0/build/ol.js"></script>
<script src="https://unpkg.com/ol-rotate-feature@latest/dist/ol-rotate-feature.umd.js"></script>
<script>
  // plugin exports global variable RotateFeatureInteraction
  // in addition it also exported to `ol.interaction.RotateFeature` field (for backward compatibility).
</script>
```

### Options

| Option    | Type                                                                                               | Description                                                                                                                                                                                 |
| :-------- | :------------------------------------------------------------------------------------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| features  | _ol.Collection<ol.Feature>_                                                                        | The features the interaction works on. **Required**.                                                                                                                                        |
| style     | _ol.style.Style &#124; Array&lt;ol.style.Style&gt; &#124; ol.style.StyleFunction &#124; undefined_ | Style of the overlay with interaction helper features.                                                                                                                                      |
| angle     | _number &#124; undefined_                                                                          | Initial angle in radians (positive is counter-clockwise), applied for features already added to collection. Default is `0`.                                                                 |
| anchor    | _number[] &#124; ol.Coordinate &#124; undefined_                                                   | Initial anchor coordinate. Default is center of features extent.                                                                                                                            |
| condition | _module:ol/events/condition~Condition_                                                             | A function that takes an `module:ol/MapBrowserEvent~MapBrowserEvent` and returns a boolean to indicate whether that event should be handled. Default is `module:ol/events/condition~always` |

### Methods

```js
// Set current angle of interaction features.
RotateFeatureInteraction.prototype.setAngle(angle : number)
```

```js
// Returns current angle of interaction features.
RotateFeatureInteraction.prototype.getAngle() : number
```

```js
// Set current anchor position.
RotateFeatureInteraction.prototype.setAnchor(anchor? : number[] | ol.Coordinate)
```

```js
// Returns current anchor position.
RotateFeatureInteraction.prototype.getAnchor() : number[] | ol.Coordinate | undefined 
```

### Events

All events triggered by the interaction are instances of `RotateFeatureEvent`.

##### Members

- **features**    _ol.Collection_     The features being rotated.
- **angle**       _number_            Current angle in radians.
- **anchor**      _ol.Coordinate_     Current anchor position.

| Event       | Arguments            | Description                          |
| :---------- | :------------------- | :----------------------------------- |
| rotatestart | _RotateFeatureEvent_ | Triggered upon feature rotate start. |
| rotating    | _RotateFeatureEvent_ | Triggered upon feature rotating.     |
| rotateend   | _RotateFeatureEvent_ | Triggered upon feature rotation end. |

### Example usage:

```js
import { Map, View, Feature } from 'ol'
import { Tile as TileLayer, Vector as VectorLayer } from 'ol/layer'
import { OSM as OSMSource, Vector as VectorSource } from 'ol/source'
import { Point, LineString, Polygon } from 'ol/geom'
import { Select as SelectInteraction } from 'ol/interaction'
import RotateFeatureInteraction from 'ol-rotate-feature'

const point = new Feature({
  name: 'point',
  geometry: new Point([ 2384267.0573564973, 7557371.884852641 ])
})
const line = new Feature({
  name: 'line',
  geometry: new LineString([ [ -603697.2100018249, -239432.60826165066 ], [ 4190433.20404443, 2930563.8287811787 ] ])
})
const polygon = new Feature({
  name: 'polygon',
  geometry: new Polygon([ [
    [ -14482348.171434438, 6661491.741627443 ],
    [ -9541458.663080638, 6221214.458704827 ],
    [ -11473786.738129886, 3300708.4819848104 ],
    [ -14482348.171434438, 6661491.741627443 ]
  ] ])
})

const map = new Map({
  view: new View({
    center: [ 0, 0 ],
    zoom: 2
  }),
  layers: [
    new TileLayer({
      source: new OSMSource()
    }),
    new VectorLayer({
      source: new VectorSource({
        projection: 'EPSG:33857',
        features: [ point, line, polygon ]
      })
    })
  ],
  target: 'map',
  projection: 'EPSG:3857'
})

const select = new SelectInteraction()
select.getFeatures().extend([ point, line, polygon ])

const rotate = new RotateFeatureInteraction({
  features: select.getFeatures(),
  anchor: [ 0, 0 ],
  angle: -90 * Math.PI / 180
})

rotate.on('rotatestart', evt => console.log('rotate start', evt))
rotate.on('rotating', evt => console.log('rotating', evt))
rotate.on('rotateend', evt => console.log('rotate end', evt))

map.addInteraction(select)
map.addInteraction(rotate)
```

Example of usage in Browser environment in [test/umd.html](https://github.com/ghettovoice/ol-rotate-feature/tree/master/test/umd.html).

Getting total angle or last anchor coordinates after rotation:

```js
rotate.on('rotateend', evt => {
    // get total angle in degrees
    console.log(evt.angle + ' is '+ (-1 * evt.angle * 180 / Math.PI ) + '°')
    // get last anchor coordinates
    console.log(evt.anchor)
})
```

## License

MIT (c) 2016-2025, Vladimir Vershinin