How to use "keySelector" for "OrderBy()"function for sorting contours in openCV

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Hello all,

I need to find N largest area contours available in a binary image.
I wanted to try the OrderBy() function to sort the contours by Area.
However, I am unable to understand the the syntax for keySelector used as a parameter in OrderBy()

Although I am using EmguCV, but a C++ syntax will also be helpful.

Contour<Point> contours = inputImage.FindContours();
contours.Orderby( ???? ); // OrderBy(Func<Point,TKey> keySelector)

Any help is much appreciated.

Posted 26-Jul-15 20:20pm

Abhishrek

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Artem Kulikov · Accepted Answer · 2015-07-26T23:45:00

Hello.
You should notice, that in your code - you will get only one contour.
For your purpose you should fistly get all contours, and after that order them.
Check this code:

C#

var allContours = new List<Contour<Point>>();
         for (var contours = image.FindContours(); contours != null; contours = contours.HNext)
             allContours.Add(contours);
         allContours.OrderBy(x => x.Area);       // by ascending
         allContours.OrderByDescending(x => x.Area); // by descending

How to use "keySelector" for "OrderBy()"function for sorting contours in openCV

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How to use "keySelector" for "OrderBy()"function for sorting contours in openCV

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