# Install and test a simple vision app

## Verify your development environment

Before proceeding, ensure that you have successfully set up your development environment.

{% content-ref url="../../app-development/application-development" %}
[application-development](https://docs.auterion.com/app-development/app-development/application-development)
{% endcontent-ref %}

It is also recommended that you be familiar with the app development workflow.

{% content-ref url="../../app-development/application-development-1" %}
[application-development-1](https://docs.auterion.com/app-development/app-development/application-development-1)
{% endcontent-ref %}

## Download the source code

o access the application's source code, you need to be part of the Auterion Developer program. ollow [these instructions](https://docs.auterion.com/app-development/app-development) to .

{% hint style="info" %}
The ision it example is available App Examples v3.
{% endhint %}

Download the folder and extract the ision it example to your PC.

## Build and install the app

In the root directory of the example, run the following commands to build and subsequently install the app on your device:

```bash
auterion-cli app build
auterion-cli app install
```

The app `com.auterion.vision-kit-example` should now be listed in the installed apps section. You can verify that via WebUI or via the `auterion-cli app list` command.

## App functionality

The app runs a ROS2 node which performs the following steps:

1. Subscribe to image messages on the `/camera/image_raw` ROS2 topic.
2. For each YUV422-encoded image received, compute the average brightness (Y) component of all pixels in the image.
3. Publish the result on the `/image_statistics/average_brightness` ROS2 topic.

## Inspect the output

Connect to Skynode via SSH and source ROS2. You can then observe the computed average brightness component on the topic configured in the app:

```bash
pc> ssh root@10.41.1.1    #SSH into Skynode

host> docker ps     #Copy the container ID for the desired app
host> docker exec -ti <container-id> /bin/bash

app> source /opt/ros/humble/setup.bash
app> ros2 topic echo /image_statistics/average_brightness
```