> For the complete documentation index, see [llms.txt](https://docs-en.kivicube.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs-en.kivicube.com/ar-open-service/image-tracking.md).

# Image Tracking

## Summary

Provide a Class externally, owned relative functional API.

![](/files/-MEakve0nHIkVrEW3mDJ)

## Marker Tracking

### Init

Resources required to initialize tracking.

| Parameter    | Constraint | Available value      | Introduction                          |
| ------------ | ---------- | -------------------- | ------------------------------------- |
| Track Width  | Required   | Int. 320, 480 or 720 | Width value of tracked image data.    |
| Track Height | Required   | Int. Arbitrary value | Width value of tracked image data.    |
| Vertical FoV | Required   | Float. Suggest 40deg | Field of view of the tracking matrix. |

Return value: Promise. Resolve presents Initialization successful, reject presents Initialization failed.

### Set Marker

Set the identification map data to be tracked.

| Parameter | Constraint | Available value | Introduction                          |
| --------- | ---------- | --------------- | ------------------------------------- |
| Marker    | Required   | Array Buffer    | Identification map data to be tracked |

Return value: marker Id: Int. Identification map Id.

### Remove All Marker

Remove all identification map data.

| Parameter | Constraint | Available value | Introduction |
| --------- | ---------- | --------------- | ------------ |
| Null      |            |                 |              |

Return value: Null

### Do Track

Track a certain camera frame.

| Parameter    | Constraint | Available value | Introduction              |
| ------------ | ---------- | --------------- | ------------------------- |
| Camera Frame | Required   | Array Buffer    | Certain camera frame data |

Return value: track Matrix: Object { tx, ty, tz, rxx, rxy, rxz, ryx, ryy, ryz, rzx, rzy, rzz, marker Id } | null. 

When return to track Matrix, it presents identification map data to be tracked; when return to null, it presents identification map data not to be tracked.

## Sample Code

```
const markerTracking = new MarkerTracking();

const trackWidth = 320;
const trackHeight = 320 / (window.innerWidth / window.innerHeight);
await markerTracking.init(trackWidth, trackHeight, 40);

const markerAb = await fetch("https://domain.com/path/to/marker.marker").then(res => res.arraybuffer());
const markerId = markerTracking.setMarker(markerAb);

function getCameraFrameArrayBuffer() {
    const frame = new ArrayBuffer(trackWidth * trackHeight * 4);

    // @TODO Acquire camera frame data by yourself

    return frame;
}

function tracking() {
    const cameraFrame = getCameraFrameArrayBuffer();
    const trackInfo = markerTracking.doTrack(cameraFrame);
    if (trackInfo) {
        const matrix = new Matrix4();
        matrix.set(
            trackInfo.rxx, trackInfo.rxy, trackInfo.rxz, trackInfo.tx,
            -trackInfo.ryx, -trackInfo.ryy, -trackInfo.ryz, trackInfo.ty,
            -trackInfo.rzx, -trackInfo.rzy, -trackInfo.rzz, trackInfo.tz,
            0.0, 0.0, 0.0, 1.0);

        if (markerId === trackInfo.markerId) {
            // @TODO
        }
    }

    requestAnimationFrame(tracking);
};

tracking();
```


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