razgriz's profile - activity

Good day. Sorry for the long title, I even had to cut it down since I was exceeding the 150 character limit.

I am building an Android Application and I want to be able to detect black circles. I am using OpenCV3 for Android and I am able to filter out the black colours from my camera feed using the code below. Kindly note that I used the Color-blob-detection example given in the Android SDK and tweaked the code as such:

public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {
    mRgba = inputFrame.rgba();

    if (mIsColorSelected) {

        Bitmap resultBitmap;

        resultBitmap = Bitmap.createBitmap(mRgba.cols(), mRgba.rows(),Bitmap.Config.ARGB_8888);
        Utils.matToBitmap(mRgba, resultBitmap);

        //TODO - look for circles
        Mat mat = new Mat(resultBitmap.getWidth(), resultBitmap.getHeight(), CvType.CV_8UC1);
        Utils.bitmapToMat(resultBitmap, mat);

        final Bitmap bitmap;

        //TODO - filter out the black only
        Mat mHSV = mat;
        Mat mHSVThreshed = mat;
        Mat mRgba2 = mat;

        Imgproc.cvtColor(mat, mHSV, Imgproc.COLOR_BGR2HSV, 0);
        Core.inRange(mHSV, new Scalar(0, 0, 0), new Scalar(130, 130, 130), mHSVThreshed);
        Imgproc.cvtColor(mHSVThreshed, mat, Imgproc.COLOR_GRAY2BGR, 0);
        Imgproc.cvtColor(mat, mRgba2, Imgproc.COLOR_BGR2RGBA, 0);

        Imgproc.GaussianBlur(mRgba2, mRgba2, new Size(9, 9), 2, 2);

        //this is for displaying purposes only. 
        //At this point, the image would be black and white, where the white spots are the black detected blobs 
        //            Bitmap bmp = Bitmap.createBitmap(mRgba2.cols(), mRgba2.rows(), Bitmap.Config.ARGB_8888);
        //Utils.matToBitmap(mRgba2, bmp);
       //bitmap = bmp; //resultBitmap;

        //TODO - new circle detection code: this uses the colour filtered Mat
        mat = mRgba2;
        Imgproc.HoughCircles(mat, circles,
                Imgproc.CV_HOUGH_GRADIENT, 1, minDist, 100,
                20, 0, 0);

        /* get the number of circles detected */
        int numberOfCircles = (circles.rows() == 0) ? 0 : circles.cols();

        /* draw the circles found on the image */
        for (int i = 0; i < numberOfCircles; i++) {

        /* get the circle details, circleCoordinates[0, 1, 2] = (x,y,r)
         * (x,y) are the coordinates of the circle's center
         */

            double[] circleCoordinates = circles.get(0, i);

            int x = (int) circleCoordinates[0], y = (int) circleCoordinates[1];

            Point center = new Point(x, y);
            int radius = (int) circleCoordinates[2];

            /* circle's outline */
            Imgproc.circle(mRgba2, center, radius, new Scalar(0,
                    200, 255), 4);

            /* circle's center outline */
            Imgproc.rectangle(mRgba2, new Point(x - 5, y - 5),
                    new Point(x + 5, y + 5),
                    new Scalar(0, 200, 255), -1);
        }
        Utils.matToBitmap(mRgba2, resultBitmap);

        bitmap = resultBitmap;

        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                mOpenCvCameraView.disableView();
                mOpenCvCameraView.setVisibility(SurfaceView.GONE);
                imageView.setVisibility(View.VISIBLE);
                imageView.setImageBitmap(bitmap);
            }
        });
    }
    return mRgba;
}

What my code does is that it takes a snapshot of the camera feed as a Mat, and then using that Mat, I do some image processing on it and to black out everything except the black colour. The resulting Mat is the mRgba2 variable and I converted to Bitmap and displayed on an ImageView. I displayed this Bitmap to confirm that I am getting the result I want.

After I know that I'm able to filter out the colour I wanted, I then run a GaussianBlur on it then proceed to run HoughCircles. However, when I run the

Imgproc ...