Java : Drawing the shape of the detected object?

After detecting the people upperbody rect:

1. Remove the rect background, keeping just the person upperbody.
2. Binarize the image.
3. Apply morphological boundary algorithm to trace the upperbody.

Example:

OpenCV provides these algorithms. However, the example above was developed using Marvin. The source code is presented below:

public class TraceShape {

    public TraceShape(){
        // Load Plug-in
        MarvinImagePlugin boundary = MarvinPluginLoader.loadImagePlugin( 

        "org.marvinproject.image.morphological.boundary");

        // Load image
        MarvinImage image = MarvinImageIO.loadImage("./res/person.jpg");

        // Binarize
        MarvinImage binImage = MarvinColorModelConverter.rgbToBinary(image, 245);
        MarvinImageIO.saveImage(binImage, "./res/person_bin.png");

        // Boundary
        boundary.process(binImage.clone(), binImage);
        MarvinImageIO.saveImage(binImage, "./res/person_boundary.png");
    }

    public static void main(String[] args) {
        new TraceShape();
    }
}