Hi I'm trying to find the arbitrarily oriented bounding box of a binary image. This seems like a pretty trivial problem but I've spent 2 days trying to find the correct way to use minAreaRect() and to use it to create a simple binary mask.
Can anyone please help, in java please?
Thank you to all.
java is somewhat clumsy here, but it's just a few lines:
Mat mask = Mat.zeros(400,400,CvType.CV_8U); // all black
// your RotatedRect will come from minAreaRect(), this is just demo data !
RotatedRect rc = new RotatedRect(Point(200,200), new Size(200,100), 23);
// retrieve corner points:
Point[] p = Point[4];
rc.points(p);
// draw white, filled poly:
MatOfPoint mp = new MatOfPoint(p);
Imgproc.fillConvexPoly(mask, mp, new Scalar(255));
usually you need a contour as input for minAreaRect(), see tutorial and some conversion code (sorry, untested):
List<MatOfPoint> contours = new ArrayList<>();
Imgproc.findContours(cannyOutput, contours, ...);
Point [] pts = contours.get(i).toArray();
RotatedRect rc = Imgproc.minAreaRect(new MatOfPoint2f(pts));
sorry, i was just trying out latest 4.0, where all drawing stuff was moved to Imgproc for consistency, but yes, it's likely in Core with your version
Thanks! It works like a charm but what is the correct way to get a RotatedRect from minAreaRect? Currently this is what I'm trying to do.
MatOfPoint2f Points = new MatOfPoint2f();
Core.findNonZero(paper_mat,Points);
RotatedRect minRect=Imgproc.minAreaRect(Points);
and its not working. paper_mat is a binary image that looks basically like the image you posted just not quite so neat.
Also for brevity fillConvexPoly is in Core not Imgproc
Thanks again
Asked: 2018-09-04 08:29:38 -0600
Seen: 1,595 times
Last updated: Sep 04 '18
