Detect color with a Viam Rover

In this tutorial you will learn how to configure a color detector with the vision service and leverage that detector with a transform camera to detect the color red.

The vision service enables a robot to use its cameras to see and interpret the world around it. The service also allows you to create different types of detectors with which the robot can recognize objects, scan QR codes, perform optical quality inspections, sort different colored objects, take measurements, and more.

You can follow this tutorial with a rented Viam Rover or with your own Viam Rover.

Enable the cameras

Before configuring color detection, enable the rover’s camera to get a better sense of what it perceives.

• If you are running this tutorial with a rented Viam Rover, enable both provided cameras: the front-facing camera and the overhead cam. In the viam_base component panel under the Control tab, enable both the cam for the front-facing camera and the overhead-cam:overheadcam for an overhead view of your rover.

  

  You can also view and control the camera streams from the individual camera component panels.

• If you are running this tutorial on your own Viam Rover, enable the front facing camera. If you are using the ViamRover fragment with your rover, the front facing camera is named cam and can be enabled in the viam_base component panel under the Control tab.

Add the vision service to detect a color

This tutorial uses the color #7a4f5c or rgb(122, 79, 92) (a reddish color).

Hex color #7a4f5c:

Navigate to your robot’s Config tab on the Viam app and configure your vision service color detector:

"services": [
  {
    "name": "my_color_detector",
    "type": "vision",
    "model": "color_detector",
    "attributes": {
      "segment_size_px": 100,
      "detect_color": "#7a4f5c",
      "hue_tolerance_pct": 0.06
    }
  },
  ... // Other services
]

The color_detector is a heuristic-based detector that draws boxes around objects according to their hue.

Click Save config and head to the Components tab.

You cannot interact directly with the vision service. To be able to interact with the vision service you must configure a camera component.

Configure a transform camera to use the color detector

Viam camera components can be physical like the one already configured on the rover, or virtual. A virtual transform camera transforms the output from a physical camera.

To view output from the color detector overlaid on images from a physical camera, configure a transform camera:

1. Navigate to the Config tab in the Viam app and click the Components subtab.
2. Click Create component in the lower-left corner of the page.
3. Select camera as the type.
4. Select transform as the model.
5. Enter a name, for example detectionCam, and click Create.

Viam generates an Attributes section for the detection camera’s component panel:

Copy the following JSON configuration into the Attributes section:

{
  "source": "cam",
  "pipeline": [
    {
      "attributes": {
        "detector_name": "my_color_detector",
        "confidence_threshold": 0.3
      },
      "type": "detections"
    }
  ]
}

Explanations of each attribute are as follows:

• source: The name of the physical camera on the rover, which provides the visual feed to get detections from.
• pipeline: Contains the transformation objects to apply to the camera.
• attributes: The attributes of this transform camera.
  • detector_name: The name of the detector.
  • confidence_threshold: The percentage of confidence needed by the detection service to identify a color. Since we set it to 0.3, this means that detections with less than 30% confidence won’t be recognized.
  • type: The type of transform camera.

The filled-in transform camera configuration panel will look like this:

After adding the component and its attributes, click Save config.

Test your transform camera in the Control tab

In the Control tab, click on your base component and enable the detection camera in the Live Feeds section.

Next, enable the keyboard and move your rover around until your camera detects the specified color.

Each time the camera detects the color, you will see a red rectangle around the color labeled with the detection confidence level.

Scroll down in the Control tab and select the dedicated section for detectionCam to access its live stream.

Next Steps

If you’re ready for more, try making your rover detect other colors. You could also write some code with a Viam SDK to make your Viam Rover move in a square.

You can also ask questions in the Community Discord and we will be happy to help.