not detecting filled circle, showing empty circle instead- Opencv

Question

I am new to OpenCV and trying to make omr scanner from scratch and have snippet which is supposed to detect filled circles but it is doing quite opposite and detecting unfilled circle. Please show me my mistake in the code.

public void showFilledCircles(Bitmap paramView)
{
    paramView = BitmapFactory.decodeFile(filename);
    Mat localMat1 = new Mat();
    Utils.bitmapToMat(paramView, localMat1);
    Object localObject1 = new Mat();
    double[] lo;
    Imgproc.GaussianBlur(localMat1, (Mat)localObject1, new Size(3.0D, 3.0D), 3.0D, 2.5D);
    Mat localMat2 = new Mat();
    Imgproc.cvtColor((Mat)localObject1, localMat2, 7);
    localObject1 = new ArrayList();
    Object localObject2 = new Mat();
    Mat localMat3 = new Mat();
    Imgproc.Canny(localMat2, localMat3, 140.0D, 255.0D);
    Imgproc.findContours(localMat3, (List)localObject1, (Mat)localObject2,1,2);
    int i = 0;
    while (i < ((List)localObject1).size())
    {
        Imgproc.drawContours(localMat2, (List)localObject1, i, new Scalar(0.0D, 0.0D, 255.0D), 2);
        //Log.i("Local Objects","Local Object Point -------------------"+localMat2);
        i += 1;
    }
    localObject1 = new Mat();
    Core.inRange(localMat2, new Scalar(70.0D, 70.0D, 70.0D), new Scalar(255.0D, 255.0D, 255.0D), (Mat)localObject1);
    localMat2 = localMat1.clone();
    Imgproc.HoughCircles((Mat)localObject1, localMat2, 3, 1.0D, 20.0D, 40.0D, 10.0D, 6, 18);

i = 0;
for (;;)
{
    if (i < localMat2.cols())
    {
        localObject1 = localMat2.get(0, i);
        lo = localMat2.get(0, i);
        if (localObject1 != null) {}
    }
    else
    {
        Utils.matToBitmap(localMat1, paramView);
        this.imageView.setImageBitmap(paramView);
        //this.imageView.setRotation(90.0F);
        return;
    }
    localObject2 = new Point(Math.round(lo[0]), Math.round(lo[1]));
    int j = (int)Math.round(lo[2]);
    Log.i("cicle Points ---------", localObject2 + " radius " + j);
    Imgproc.circle(localMat1, (Point)localObject2, 1, new Scalar(0.0D, 0.0D, 255.0D), 5);
    Imgproc.circle(localMat1, (Point)localObject2, j, new Scalar(255.0D, 0.0D, 0.0D), 5);
    i += 1;
}
}

output image

Abhishek · Accepted Answer · 2017-07-31 09:38:22Z

0

for more precise detection of filled circle.

step 1: detect contours on image

step 2: create rectangle around detected contours.

step 3: depending on rectangle height and width choose only those contours which you want.

for filled circle detection refer to this question Detect filled circle using opencv4Android

answered Jul 31, 2017 at 9:38

Abhishek

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