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    <p>cv::findcontours returns every contour as a vector of points (see <a href="http://docs.opencv.org/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html#findcontours" rel="noreferrer">http://docs.opencv.org/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html#findcontours</a>).</p> <p>You have to convert these vectors to your data structure (Component) by yourself like in this minimal example I created:</p> <pre><code>#include &lt;opencv2/opencv.hpp&gt; #include &lt;iostream&gt; struct Component { cv::Rect boundingBox; double area; double circularity; }; int main() { // Create a small image with a circle in it. cv::Mat image(256, 256, CV_8UC3, cv::Scalar(0, 0, 0)); cv::circle(image, cv::Point(80, 110), 42, cv::Scalar(255,127, 63), -1); // Find canny edges. cv::Mat cannyEdges; cv::Canny(image, cannyEdges, 80, 60); // Show the images. cv::imshow("img", image); cv::imshow("cannyEdges", cannyEdges); // Find the contours in the canny image. cv::vector&lt;cv::Vec4i&gt; hierarchy; // "Each contour is stored as a vector of points." // http://docs.opencv.org/modules/imgproc/doc/structural_analysis_and_shape_descriptors.html#findcontours typedef cv::vector&lt;cv::vector&lt;cv::Point&gt; &gt; TContours; TContours contours; cv::findContours(cannyEdges, contours, hierarchy, CV_RETR_CCOMP, CV_CHAIN_APPROX_NONE); // cannyEdges is destroyed after calling cv::findContours // Print number of found contours. std::cout &lt;&lt; "Found " &lt;&lt; contours.size() &lt;&lt; " contours." &lt;&lt; std::endl; // Convert contours to Components. typedef cv::vector&lt;Component&gt; TComponents; TComponents components; for (TContours::const_iterator it( contours.begin() ); it != contours.end(); ++it) { Component c; c.area = cv::contourArea(*it); c.boundingBox = cv::boundingRect(*it); c.circularity = 0.0; // Insert whatever you mean by circularity; components.push_back(c); } for (TComponents::const_iterator it( components.begin() ); it != components.end(); ++it) std::cout &lt;&lt; it-&gt;area &lt;&lt; std::endl; // and whatever you want. // Wait for user input. cv::waitKey(); } </code></pre>
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    1. CODear Dobi: thank you very much for your answer. I tried your code, and it gives out an error for the line "typedef cv::vector (...)", saying "Error: argument list for class template "std::vector" is missing ". Sorry for my late reply, due to internet access problem.
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    2. COI guess you are using an older compiler, that does not support >> in template types. I corrected this in the code above, i.g. I made "typedef cv::vector<cv::vector<cv::Point>> TContours;" to "typedef cv::vector<cv::vector<cv::Point> > TContours;". Please try again therewith.
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    3. COthank you very much! now it works fine.
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