Configure and execute ArUcoCamera
=================================

Once [ArUco markers are placed into a scene](aruco_scene_creation.md) and [the camera optic have been calibrated](optic_parameters_calibration.md), everything is ready to setup an ArUco marker pipeline thanks to [ArUcoCamera](../../argaze.md/#argaze.ArUcoMarkers.ArUcoCamera) class.

As it inherits from [ArFrame](../../argaze.md/#argaze.ArFeatures.ArFrame), the [ArUcoCamera](../../argaze.md/#argaze.ArUcoMarkers.ArUcoCamera) class benefits from all the services of a [gaze analysis pipeline](./user_guide/gaze_analysis_pipeline/introduction.md). Besides, the [ArUcoCamera](../../argaze.md/#argaze.ArUcoMarkers.ArUcoCamera) class projects [ArUcoScenes](../../argaze.md/#argaze.ArUcoMarkers.ArUcoScene)'s layers into its own layers thanks to ArUco markers pose estimations made by its [ArUcoDetector](../../argaze.md/#argaze.ArUcoMarkers.ArUcoDetector).

![ArUco camera frame](../../img/aruco_camera_frame.png)

## Load JSON configuration file

The [ArUcoCamera](../../argaze.md/#argaze.ArUcoMarkers.ArUcoCamera) internal pipeline loads from a JSON configuration file thanks to [ArUcoCamera.from_json](../../argaze.md/#argaze.ArUcoMarkers.ArUcoCamera.from_json) class method. 

Here is a simple JSON ArUcoCamera configuration file example:

```json
{
	"name": "My FullHD camera",
	"size": [1920, 1080],
	"aruco_detector": {
        "dictionary": {
            "name": "DICT_APRILTAG_16h5"
        },
        "marker_size": 5,
        "optic_parameters": "optic_parameters.json",
    },
    "scenes": {
        "main_scene" : {
            "aruco_markers_group": "aruco_description.json"
        }
    },
    "image_parameters": {
        "background_weight": 1,
        "draw_detected_markers": {
            "color": [0, 255, 0],
            "draw_axes": {
                "thickness": 3
            }
        }
    }
}
```

Then, here is how to load the JSON file:

```python
from argaze.ArUcoMarkers import ArUcoCamera

# Load ArUcoCamera
aruco_camera = ArUcoCamera.ArUcoCamera.from_json('./configuration.json')
```

Now, let's understand the meaning of each JSON entry.

### Name (inherited from ArFrame)

The name of the [ArUcoCamera](../../argaze.md/#argaze.ArUcoMarkers.ArUcoCamera) frame. Basically useful for visualisation purpose.

### Size (inherited from ArFrame)

The size of the [ArUcoCamera](../../argaze.md/#argaze.ArUcoMarkers.ArUcoCamera) frame  in pixels. Be aware that gaze positions have to be in the same range of value.

### ArUco detector

...

### Scenes

...

### Image parameters (inherited from ArFrame)

...

## Pipeline execution

Timestamped gaze positions have to be passed one by one to [ArFrame.look](../../argaze.md/#argaze.ArFeatures.ArFrame.look) method to execute the whole intanciated pipeline.

```python
# Assuming that live Full HD (1920x1080) video stream is enabled
...

# Assuming there is a way to escape the while loop
...

    while video_stream.is_alive():

        # Capture image from video stream
        image = video_stream.read()

        # Detect ArUco markers in image
        aruco_camera.watch(image)

        # Do something with ArUcoCamera frame image
        ...
```