opencv for processing convexity defects example

hand_tracking_convexity_defects.pde

import gab.opencv.*;
import org.opencv.imgproc.Imgproc;
import org.opencv.core.Mat;
import org.opencv.core.MatOfInt;
import org.opencv.core.MatOfInt4;

import org.opencv.core.MatOfPoint;

import java.awt.Rectangle;
import java.util.Arrays;

PImage src, dst;
OpenCV opencv;

ArrayList<Contour> contours;
ArrayList<Contour> polygons;

ArrayList<PVector> defectPoints;
ArrayList<Float> depths;
ArrayList<PVector> handPoints;

Contour convexHull;
PVector hullCenter;
void setup() {
  src = loadImage("white_hand.jpg"); 
  size(src.width, src.height/2, P2D);
  opencv = new OpenCV(this, src);

  opencv.blur(5);
  opencv.inRange(80, 180);

  dst = opencv.getOutput();
  contours = opencv.findContours(false, true);

  Contour contour = contours.get(0);
  convexHull = contour.getPolygonApproximation().getConvexHull();

  hullCenter = new PVector(convexHull.getBoundingBox().x + convexHull.getBoundingBox().width/2, 
  convexHull.getBoundingBox().y + convexHull.getBoundingBox().height/2);


  MatOfInt hull = new MatOfInt();
  MatOfPoint points = new MatOfPoint(contours.get(0).pointMat);
  Imgproc.convexHull(points, hull);

  MatOfInt4 defects = new MatOfInt4();
  Imgproc.convexityDefects(points, hull, defects );

  defectPoints  = new ArrayList<PVector>();
  depths =  new ArrayList<Float>(); 

  ArrayList<Integer> defectIndices = new ArrayList<Integer>();
  
  for (int i = 0; i < defects.height(); i++) {

    int startIndex = (int)defects.get(i, 0)[0];
    int endIndex = (int)defects.get(i, 0)[1];
    int defectIndex = (int)defects.get(i, 0)[2];
    if (defects.get(i, 0)[3] > 10000) {
      defectIndices.add( defectIndex );
      defectPoints.add(contour.getPoints().get(defectIndex));
      depths.add((float)defects.get(i, 0)[3]);
    }
  }
//  
  Integer[] handIndices = new Integer[defectIndices.size() + hull.height()];
  for (int i = 0 ; i < hull.height(); i++) {
    handIndices[i] = (int)hull.get(i, 0)[0];
  }
  for(int d = 0; d < defectIndices.size(); d++){
    handIndices[d + hull.height()] = defectIndices.get(d);
  }

  Arrays.sort(handIndices);
  println(handIndices);
  handPoints = new ArrayList<PVector>();
  for(int i = 0; i < handIndices.length; i++){
    handPoints.add(contour.getPoints().get(handIndices[i]));
  }
}


void draw() {
  scale(0.5);
  image(src, 0, 0);
  image(dst, src.width, 0);

  noFill();
  strokeWeight(3);
  stroke(0, 255, 0);
  contours.get(0).draw();

  stroke(255, 0, 0);
  convexHull.draw();

  stroke(0, 0, 255);
  fill(255);
  for (PVector p : defectPoints) {
     ellipse(p.x, p.y, 20,20);
  }

  pushStyle();
  fill(255);
  stroke(255, 0, 0);
  ellipse(hullCenter.x, hullCenter.y, 30, 30);

  popStyle();
  
  stroke(0,0,255);
  noFill();
  beginShape();
  for(PVector p : handPoints){
    vertex(p.x,p.y);
  }
  endShape(CLOSE);
}