"Fossies" - the Fresh Open Source Software Archive

Member "opencv-2.4.11/doc/tutorials/imgproc/shapedescriptors/moments/moments.rst" (25 Feb 2015, 3920 Bytes) of archive /linux/misc/opencv-2.4.11.zip:


As a special service "Fossies" has tried to format the requested source page into HTML format (assuming markdown format). Alternatively you can here view or download the uninterpreted source code file. A member file download can also be achieved by clicking within a package contents listing on the according byte size field.

.. _moments:

Image Moments


Goal

In this tutorial you will learn how to:

.. container:: enumeratevisibleitemswithsquare

Theory

Code

This tutorial code’s is shown lines below. You can also download it from here <https://github.com/Itseez/opencv/tree/master/samples/cpp/tutorial_code/ShapeDescriptors/moments_demo.cpp>_

.. code-block:: cpp

#include “opencv2/highgui/highgui.hpp” #include “opencv2/imgproc/imgproc.hpp” #include #include <stdio.h> #include <stdlib.h>

using namespace cv; using namespace std;

Mat src; Mat src_gray; int thresh = 100; int max_thresh = 255; RNG rng(12345);

/// Function header void thresh_callback(int, void* );

/ @function main */ int main( int argc, char argv ) { /// Load source image and convert it to gray src = imread( argv[1], 1 );

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

 /// Create Window
 char* source_window = "Source";
 namedWindow( source_window, CV_WINDOW_AUTOSIZE );
 imshow( source_window, src );

 createTrackbar( " Canny thresh:", "Source", &thresh, max_thresh, thresh_callback );
 thresh_callback( 0, 0 );

 waitKey(0);
 return(0);

}

/ @function thresh_callback / void thresh_callback(int, void ) { Mat canny_output; vector<vector > contours; vector hierarchy;

 /// Detect edges using canny
 Canny( src_gray, canny_output, thresh, thresh*2, 3 );
 /// Find contours
 findContours( canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );

 /// Get the moments
 vector<Moments> mu(contours.size() );
 for( int i = 0; i < contours.size(); i++ )
    { mu[i] = moments( contours[i], false ); }

 ///  Get the mass centers:
 vector<Point2f> mc( contours.size() );
 for( int i = 0; i < contours.size(); i++ )
    { mc[i] = Point2f( mu[i].m10/mu[i].m00 , mu[i].m01/mu[i].m00 ); }

 /// Draw contours
 Mat drawing = Mat::zeros( canny_output.size(), CV_8UC3 );
 for( int i = 0; i< contours.size(); i++ )
    {
      Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
      drawContours( drawing, contours, i, color, 2, 8, hierarchy, 0, Point() );
      circle( drawing, mc[i], 4, color, -1, 8, 0 );
    }

 /// Show in a window
 namedWindow( "Contours", CV_WINDOW_AUTOSIZE );
 imshow( "Contours", drawing );

 /// Calculate the area with the moments 00 and compare with the result of the OpenCV function
 printf("\t Info: Area and Contour Length \n");
 for( int i = 0; i< contours.size(); i++ )
    {
      printf(" * Contour[%d] - Area (M_00) = %.2f - Area OpenCV: %.2f - Length: %.2f \n", i, mu[i].m00, contourArea(contours[i]), arcLength( contours[i], true ) );
      Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );
      drawContours( drawing, contours, i, color, 2, 8, hierarchy, 0, Point() );
      circle( drawing, mc[i], 4, color, -1, 8, 0 );
    }

}

Explanation

Result

. Here it is:

========== ========== ========== |MU_0| |MU_1| |MU_2| ========== ========== ==========

.. |MU_0| image:: images/Moments_Source_Image.jpg :width: 250pt :align: middle

.. |MU_1| image:: images/Moments_Result1.jpg :width: 250pt :align: middle

.. |MU_2| image:: images/Moments_Result2.jpg :width: 250pt :align: middle