c# - Ignore external points when finding rectangles -


i have images need find central rectangle

enter image description here

im using variation of emgucv examples find rectangles , came this

using (memstorage storage = new memstorage()) { //allocate storage contour approximation      //contour<point> contours = gray.findcontours()     contour<point> contours = gray.findcontours(emgu.cv.cvenum.chain_approx_method.cv_chain_approx_simple,      emgu.cv.cvenum.retr_type.cv_retr_list,   storage);      (; contours != null; contours = contours.hnext)     {         contour<point> currentcontour = contours.approxpoly(contours.perimeter * 0.05, storage);         //seq<point> currentcontour = contours.getconvexhull(emgu.cv.cvenum.orientation.cv_clockwise);          if (contours.area > minrectanglearea) //only consider contours area greater 20000         {             if (currentcontour.total == 4) //the contour has 4 vertices.             {                 bool isrectangle = true;                 point[] pts = currentcontour.toarray();                 linesegment2d[] edges = pointcollection.polyline(pts, true);                  (int = 0; < edges.length; i++)                 {                     double angle = math.abs(edges[(i + 1) % edges.length].getexteriorangledegree(edges[i]));                     if (angle < 90 - rectangleanglemargin  || angle > rectangleanglemargin + 90)                     {                         isrectangle = false;                         break;                     }                 }                  if (isrectangle)                 {                     boxlist.add(currentcontour.getminarearect());                 }             }         }     }

}

and result of executing on images finds 2 rectangles:

enter image description here

the orange rectangle ok, thats need. dont want blue. 4 vertex in border of image, 1 of them out.

changing retr_type of findcontours function cv_retr_external, blue rectangle, wonder if there option of not getting contours external points.

the real image can have smaller rectangles inside orange (or line appears splitting rectangle), after i´m selecting bigger rectangle 1 want, cant way blue one.

taking @ sample image choose approach.

instead of classical contour detection, if perform hough line detection , peform intersections of line found, find 4 vertices of rectangle searching for...

if need in coding let me know , edit answer.


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