Hello OpenCV Community,
I'm currently trying to close the contours on the right of this picture: PIC . The reason for the opened contour lies in kabeja, a library to convert DXF files to images. It seems that on some images it doesn't convert the last pixel column (or row) and thats why the Sample picture is open.
I had the idea to use Core.copyMakeBorder() in Opencv, to add some space to the picture. After that I tried to use Imgproc.approxPolyDP() to close the contour, but this doesn't work. I tried this with different Epsilon values: PICs
The reason for that is maybe that the contour surrounds the line. It never closes the contour where i want it to do.
I tried another method using Imgproc.convexHull(), which delivers this one: PIC. This could be useful for me, but i have no idea how to take out the part of the convex hull i need and merge it together with the contour to close it.
I hope that someone has an idea.
Here is my method for Imgproc.approxPolyDP()
public static ArrayList<MatOfPoint> makeComplete(Mat mat) {
System.out.println("makeComplete: START");
Mat dst = new Mat();
Core.copyMakeBorder(mat, dst, 10, 10, 10, 10, Core.BORDER_CONSTANT);
ArrayList<MatOfPoint> cnts = Tools.getContours(dst);
ArrayList<MatOfPoint2f> opened = new ArrayList<>();
//convert to MatOfPoint2f to use approxPolyDP
for (MatOfPoint m : cnts) {
MatOfPoint2f temp = new MatOfPoint2f(m.toArray());
opened.add(temp);
System.out.println("First loop runs");
}
ArrayList<MatOfPoint> closed = new ArrayList<>();
for (MatOfPoint2f conts : opened) {
MatOfPoint2f temp = new MatOfPoint2f();
Imgproc.approxPolyDP(conts, temp, 3, true);
MatOfPoint closedTemp = new MatOfPoint(temp.toArray());
closed.add(closedTemp);
System.out.println("Second loop runs");
}
System.out.println("makeComplete: END");
return closed;
}
And here the code for Imgproc.convexHull()
public static ArrayList<MatOfPoint> getConvexHull(Mat mat) {
Mat dst = new Mat();
Core.copyMakeBorder(mat, dst, 10, 10, 10, 10, Core.BORDER_CONSTANT);
ArrayList<MatOfPoint> cnts = Tools.getContours(dst);
ArrayList<MatOfPoint> out = new ArrayList<MatOfPoint>();
MatOfPoint mopIn = cnts.get(0);
MatOfInt hull = new MatOfInt();
Imgproc.convexHull(mopIn, hull, false);
MatOfPoint mopOut = new MatOfPoint();
mopOut.create((int) hull.size().height, 1, CvType.CV_32SC2);
for (int i = 0; i < hull.size().height; i++) {
int index = (int) hull.get(i, 0)[0];
double[] point = new double[]{
mopIn.get(index, 0)[0], mopIn.get(index, 0)[1]
};
mopOut.put(i, 0, point);
}
out.add(mopOut);
return out;
}
I will edit this post to add the pictures after I have the rights for it to do.
Best regards, Brk
