First off, I am using the OpenCV 3.1.0 Java wrapper (NOT JavaCV).
I am trying to find the convexity defects on a hand, but it is not giving the expected results. For examples, here is a binary image of a hand:
(The white lines show the convex hull, and the blue lines show the contour that I am working with).
Here is the same image showing the attempted convexity defect detection:
(blue dots show defects, and pink lines show the resulting shape)
As you can see, the defect between the index and thumb is not being detected.
Here is my code:
...
hull = new MatOfInt();
Imgproc.convexHull(approxContour, hull, false);
MatOfInt4 defects = new MatOfInt4();
Imgproc.convexityDefects(approxContour, hull, defects);
numPoints = defects.total();
if (numPoints > max_points) {
System.out.println("Processing " + max_points + " defect pts");
numPoints = max_points;
}
for (int i = 0; i < numPoints; i++) {
double[] dat = defects.get(i, 0);
double[] startdat = approxContour.get((int) dat[0], 0);
Point startPt = new Point(startdat[0], startdat[1]);
tipPts[i] = startPt;
double[] enddat = approxContour.get((int) dat[1], 0);
endPts[i] = new Point(enddat[0], enddat[1]);
double[] depthdat = approxContour.get((int) dat[2], 0);
Point depthPt = new Point(depthdat[0], depthdat[1]);
foldPts[i] = depthPt;
depths[i] = dat[3];
}
...
for (int i = 0; i < numPoints; i++) {
Imgproc.circle(im, tipPts[i], 2, new Scalar(0, 0, 255));
Imgproc.circle(im, foldPts[i], 2, new Scalar(255, 0, 0));
Imgproc.circle(im, endPts[i], 2, new Scalar(0, 255, 0));
Imgproc.line(im, tipPts[i], foldPts[i], new Scalar(255, 0, 255));
Imgproc.line(im, tipPts[i], endPts[i], new Scalar(255, 255, 255));
Imgproc.line(im, endPts[i], foldPts[i], new Scalar(255, 0, 255));
}
