CODEWITHSUNDEEP
xcodeopencv
sri
sri

Reputation: 227

Detect Only Circles using OpenCV

I am using the following code to detect the circles only . But it is also detecting the other shapes . Please help to do this . I have used the HoughCircles but it is not giving the Good results. My requirement is have to detect the circles only .

Mat src, src_gray;

/// Read the image
src = t2;

if(! src.data )                              // Check for invalid input
{
    cout <<  "Could not open or find the image" << std::endl ;
    cv::waitKey(5000);
}

/// Convert it to gray
cvtColor( src, src_gray, CV_BGR2GRAY );
blur( src_gray, src_gray, Size(3,3) );

/// Reduce the noise so we avoid false circle detection
GaussianBlur( src_gray, src_gray, Size(9, 9), 2, 2 );


Mat src_lines; Mat src_gray_lines;
int thresh_lines = 100;
RNG rng_lines(12345);

Mat threshold_output;
vector<vector<Point> > contours;
vector<Vec4i> hierarchy;

src_gray_lines = src_gray;
/// Detect edges using Threshold
threshold( src_gray_lines, threshold_output, thresh_lines, 255, THRESH_BINARY );
/// Find contours
findContours( threshold_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );

/// Find the rotated rectangles and ellipses for each contour
vector<RotatedRect> minRect( contours.size() );
vector<RotatedRect> minEllipse( contours.size() );

for( size_t i = 0; i < contours.size(); i++ )
{
    minRect[i] = minAreaRect( Mat(contours[i]) );
}

/// Draw contours + rotated rects + ellipses
Mat drawing = Mat::zeros( threshold_output.size(), CV_8UC3 );
for( size_t i = 0; i< contours.size(); i++ )
{
    // rotated rectangle
    Point2f rect_points[4];
    minRect[i].points( rect_points );
    for( int j = 0; j < 4; j++ )
        line( src, rect_points[j], rect_points[(j+1)%4], Scalar(255,0,0), 1, 8 );
}

Please let me know if my question is not clear .

Upvotes: 0

Views: 794

Answers (1)

krzych
krzych

Reputation: 2176

You have contour vectors so you can easily check their length. Circle has also area. Circle shape should have specific ratio area to length (you should compute what this ratio should be). Now eliminating shapes which does not fit this ratio (with some delta) you are getting only circles.

Upvotes: 2

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