mirror of
https://github.com/opencv/opencv.git
synced 2024-12-05 01:39:13 +08:00
be63ce723f
updated links in cheatsheet renamed directory for Mat tutorial changed links from willow docs to opencv.itseez.com, from Trac to current Redmine
137 lines
3.9 KiB
ReStructuredText
137 lines
3.9 KiB
ReStructuredText
.. _moments:
|
|
|
|
|
|
Image Moments
|
|
**************
|
|
|
|
Goal
|
|
=====
|
|
|
|
In this tutorial you will learn how to:
|
|
|
|
.. container:: enumeratevisibleitemswithsquare
|
|
|
|
* Use the OpenCV function :moments:`moments <>`
|
|
* Use the OpenCV function :contour_area:`contourArea <>`
|
|
* Use the OpenCV function :arc_length:`arcLength <>`
|
|
|
|
Theory
|
|
======
|
|
|
|
Code
|
|
====
|
|
|
|
This tutorial code's is shown lines below. You can also download it from `here <http://code.opencv.org/svn/opencv/trunk/opencv/samples/cpp/tutorial_code/ShapeDescriptors/moments_demo.cpp>`_
|
|
|
|
.. code-block:: cpp
|
|
|
|
#include "opencv2/highgui/highgui.hpp"
|
|
#include "opencv2/imgproc/imgproc.hpp"
|
|
#include <iostream>
|
|
#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<Point> > contours;
|
|
vector<Vec4i> 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
|
|
|