How can I draw rectangle with MatOfKeyPoint for Text Detection | Java
Hi guys,
I' ve been working on real time text detection and recognition with OpenCV4Android. Recognition part is totally completed. However, I have to ask question about text detection. I' m using the MSER FeatureDetector for detection text.
This is the real time and calling the method part:
public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
carrierMat = inputFrame.gray();
carrierMat = General.MSER(carrierMat);
return carrierMat;
}
And this is the basic MSER implementation:
private static FeatureDetector fd = FeatureDetector.create(FeatureDetector.MSER);
private static MatOfKeyPoint mokp = new MatOfKeyPoint();
private static Mat edges = new Mat();
public static Mat MSER(Mat mat) {
//for mask
Imgproc.Canny(mat, edges, 400, 450);
fd.detect(mat, mokp, edges);
//for drawing keypoints
Features2d.drawKeypoints(mat, mokp, mat);
return mat;
}
It works fine for finding text with edges mask.
I would like to draw a rectangles for clusters like this:
or this
You can assume that I have the right points.
As you can see, fd.detect() method is returning a MatOfKeyPoint. Hence I' ve tried this method for drawing rectangle:
public static Mat MSER_(Mat mat) {
fd.detect(mat, mokp);
KeyPoint[] refKp = mokp.toArray();
Point[] refPts = new Point[refKp.length];
for (int i = 0; i < refKp.length; i++) {
refPts[i] = refKp[i].pt;
}
MatOfPoint2f refMatPt = new MatOfPoint2f(refPts);
MatOfPoint2f approxCurve = new MatOfPoint2f();
//Processing on mMOP2f1 which is in type MatOfPoint2f
double approxDistance = Imgproc.arcLength(refMatPt, true) * 0.02;
Imgproc.approxPolyDP(refMatPt, approxCurve, approxDistance, true);
//Convert back to MatOfPoint
MatOfPoint points = new MatOfPoint(approxCurve.toArray());
// Get bounding rect
Rect rect = Imgproc.boundingRect(points);
// draw enclosing rectangle (all same color, but you could use variable i to make them unique)
Imgproc.rectangle(mat, new Point(rect.x, rect.y), new Point(rect.x + rect.width, rect.y + rect.height), Detect_Color_, 5);
//Features2d.drawKeypoints(mat, mokp, mat);
return mat;
}
But when I was trying to Imgproc.arcLength() method, it suddenly stopped. I gave a random approxDistance value for Imgproc.approxPolyDP() method like 0.1, it doesn' t work really efficiently.
So how can I draw rectangle for detected text?
Cheers!