Revision history [back]

Nice, it is working, and it is working very nice. More, your idea of resizing the mask is introducing errors, because the cv::fillPoly is introducing errors (small "stairs") and resizing it is just making the errors to appear in the new contour, and they are even bigger.

Nice, it is working, and it is working very nice. More, your idea of resizing the mask is introducing errors, because the cv::fillPoly is introducing errors (small "stairs") and resizing it is just making the errors to appear in the new contour, and they are even bigger.

#include "opencv2/imgproc.hpp"
#include "opencv2/highgui.hpp"

using namespace cv;

int main( int argc, char** argv )
{
    vector<vector<Point> > contours;
    Mat img = Mat::zeros( 500, 500, CV_8UC1 );

    circle( img, Point(250,250), 100, Scalar(255) );

    findContours( img, contours, RETR_LIST, CHAIN_APPROX_SIMPLE);

    fillConvexPoly( img, Mat( contours[0] ) / 2, Scalar(255)); // draws contour resized 1x/2

    polylines( img, Mat( contours[0] ) * 2, true, Scalar(255)); // draws contour resized 2x

    imshow("result",img);
    waitKey();

    return 0;
}

Nice, it is working, and it is working very nice. More, your idea of resizing the mask is introducing errors, because the cv::fillPoly is introducing errors (small "stairs") and resizing it is just making the errors to appear in the new contour, and they are even bigger.

Sample code :

#include "opencv2/imgproc.hpp"
#include "opencv2/highgui.hpp"

using namespace cv;

int main( int argc, char** argv )
{
    vector<vector<Point> > contours;
    Mat img = Mat::zeros( 500, 500, CV_8UC1 );

    circle( img, Point(250,250), 100, Scalar(255) );

    findContours( img, contours, RETR_LIST, CHAIN_APPROX_SIMPLE);

    fillConvexPoly( img, Mat( contours[0] ) / 2, Scalar(255)); // draws contour resized 1x/2

    polylines( img, Mat( contours[0] ) * 2, true, Scalar(255)); // draws contour resized 2x

    imshow("result",img);
    waitKey();

    return 0;
}