Skip to content
Object Color Tracker, an input feature extractor for Wekinator
C++ Makefile
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.
bin/data Fixed application icon for macOS Jun 10, 2018
Makefile Initial commit Jun 9, 2018
Project.xcconfig Initial commit Jun 9, 2018 Update Sep 29, 2018
openFrameworks-Info.plist Version bump Sep 29, 2018

Object Color Tracker


This app serves as an input feature extractor for Wekinator and allows you to use it as input device to play music, paint in the air, track people/objects on stage performance or in general, be very expressive without touching a computer.

When choosing an object (or clothes) with distinct colour (e.g. bright green), you can calibrate the colour range by holding the object in front of the camera, clicking with the mouse on the object. Then the object will be tracked. The center of the object will act as pointer with 3 axis, x, y and z. The x and y values denote the position in the window, the z value denotes the area of the object with respect to the window size and allows you to be more expressive with the output app.

Note: Only the largest detected object (blob) is used as "cursor". Other, smaller objects within calibrated colour range are ignored.

Click on the image below to see a small demo (youtube).

Demo video

Multiple camera support

Since version 1.1.0, you can cycle through available cameras by pressing the button c. In the Control Center panel is an info field that indicates the current active camera.

Calibration Settings

  • Tolerance hue / saturation / value: Allowed range outside calibration patch. Fiddle with these values until you have isolated the object from the rest of the camera feed.
  • Minimum area size: If the area inside the contour is less than this value, the detection is ignored. This helps to suppress noise.
  • Maximum area size: If the area inside the contour is greater than this value, the detection is ignored.
  • Sample radius: The patch size for measuring the colour range.
  • Low pass filter: Weak filter that adds a little bit of smoothing. Disable this feature if you think there is too much lag.

Prebuild Binary

A ready-to-run binary is available for macOS and Linux. They can be downloaded from the releases page.


  • Drag the app to the Applications folder and double click to start the program


  • Download and unpack the tar file with
tar zxvf filename.tar.gz
  • Open a terminal, go to the object-color-tracker folder and start the program with


The app is build in C++ using openFrameworks 0.10.0 and uses the following addons:

  • ofxOSC
  • ofxGui
  • ofxOpenCV
  • ofxCv

Note that ofxCv is not standard packed in openFrameworks and needs to be downloaded separately from Choose the master branch for oF 0.10.0 and stable branch if you're using oF 0.9.8. On macOS, use the ProjectGenerator to set the paths correctly and open the project with XCode.

Known Issues

  • The app does not work well in a scene with strong directional light. When e.g. the light comes only from one side, the dynamic range of the object will be too large and the app might loose track of the object when moving around in front of the camera.

  • Some cameras have quite aggressive white balance corrections. When for instance moving a green object in front of the camera, on some cameras the colour jumps continuously from too yellow to too blue and everything in between. This is very annoying since it is hard to calibrate properly so that the object is correctly detected in every white balance setting. Some fancy external cameras have "advanced features" which allows you to freeze the white balance.

    If you compile the code yourself and use macOS, you can try the following change in openFrameworks library. Edit file [of_folder]/libs/openframeworks/video/ and replace the function -(void) startCapture with:

-(void) startCapture{

	[self.captureSession startRunning];

	[captureInput.device lockForConfiguration:nil];

    if( [captureInput.device isFocusModeSupported:AVCaptureFocusModeAutoFocus] ) {
        [captureInput.device setFocusMode:AVCaptureFocusModeAutoFocus ];
    if( [captureInput.device isExposureModeSupported:AVCaptureExposureModeLocked] ) {
        NSLog(@"-- Attempt to lock exposure");
        [captureInput.device setExposureMode:AVCaptureExposureModeLocked ];
    if ([captureInput.device isWhiteBalanceModeSupported:AVCaptureWhiteBalanceModeLocked]) {
        NSLog(@"-- Attempt to lock white balance");
        [captureInput.device setWhiteBalanceMode:AVCaptureWhiteBalanceModeLocked];

Upgrading OpenCV (optional)

At the time of writing, the ofxOpenCv add-on is shipped with OpenCV version 3.1.0. If you want to run with the latest version of OpenCv you can upgrade the static library and header files in ofxOpenCv by doing these 3 steps (macOS):

  1. Install the latest version of OpenCV with brew install opencv.

  2. Run the following shell commands:

$ cp -R $OPENCV_DIR/include/*  $OPENFRAMEWORKS_DIR/addons/ofxOpenCv/libs/opencv/include/
$ libtool -static $OPENCV_DIR"/lib/lib*.a" -o $OPENFRAMEWORKS_DIR/addons/ofxOpenCv/libs/opencv/lib/osx/opencv.a

where $OPENCV_DIR points to the installation directory of OpenCV.

  1. Add OpenCL.framework to the section Linked Frameworks and Libraries.

Sorry, I don't know how to do it on Linux or Windows.


The object color tracker is created by Gilbert François Duivesteijn and distributed under GPL v2 license. The library openFrameworks is distributed under the MIT License.

You can’t perform that action at this time.