OpenCV Tutorials —— Image Moments

图像矩

Moments moments(InputArray array, bool binaryImage=false )

Parameters:

• array – Raster image (single-channel, 8-bit or floating-point 2D array) or an array ( or ) of 2D points (Point or Point2f ).
• binaryImage – If it is true, all non-zero image pixels are treated as 1’s. The parameter is used for images only.
• moments – Output moments.

C++: void HuMoments(const Moments& m, OutputArray hu)

C++: void HuMoments(const Moments& moments, double hu[7])

Parameters:

• moments – Input moments computed with moments() .
• hu – Output Hu invariants.

 

Code

#include "stdafx.h"

#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( "img3.jpg", 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 ); }	// 获取图像距

	///  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 ); }	// 图像重心

	/// 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 );
	}
}