d0/d49/tutorial_moments.html

 #include "opencv2/imgcodecs.hpp"

 #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);


 void thresh_callback(int, void* );


 int main( int, char** argv )

 {

  src = imread( argv[1], 1 );


  cvtColor( src, src_gray, COLOR_BGR2GRAY );

  blur( src_gray, src_gray, Size(3,3) );


  const char* source_window = "Source";

  namedWindow( source_window, WINDOW_AUTOSIZE );

  imshow( source_window, src );


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

  thresh_callback( 0, 0 );


  waitKey(0);

  return(0);

 }


 void thresh_callback(int, void* )

 {

  Mat canny_output;

  vector<vector<Point> > contours;

  vector<Vec4i> hierarchy;


  Canny( src_gray, canny_output, thresh, thresh*2, 3 );

  findContours( canny_output, contours, hierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0) );


  vector<Moments> mu(contours.size() );

  for( size_t i = 0; i < contours.size(); i++ )

  { mu[i] = moments( contours[i], false ); }


  vector<Point2f> mc( contours.size() );

  for( size_t i = 0; i < contours.size(); i++ )

  { mc[i] = Point2f( static_cast<float>(mu[i].m10/mu[i].m00) , static_cast<float>(mu[i].m01/mu[i].m00) ); }


  Mat drawing = Mat::zeros( canny_output.size(), CV_8UC3 );

  for( size_t i = 0; i< contours.size(); i++ )

  {

  Scalar color = Scalar( rng.uniform(0, 255), rng.uniform(0,255), rng.uniform(0,255) );

  drawContours( drawing, contours, (int)i, color, 2, 8, hierarchy, 0, Point() );

  circle( drawing, mc[i], 4, color, -1, 8, 0 );

  }


  namedWindow( "Contours", WINDOW_AUTOSIZE );

  imshow( "Contours", drawing );


  printf("\t Info: Area and Contour Length \n");

  for( size_t i = 0; i< contours.size(); i++ )

  {

  printf(" * Contour[%d] - Area (M_00) = %.2f - Area OpenCV: %.2f - Length: %.2f \n", (int)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, (int)i, color, 2, 8, hierarchy, 0, Point() );

  circle( drawing, mc[i], 4, color, -1, 8, 0 );

  }

 }

cv::Scalar
Scalar_< double > Scalar
Definition: types.hpp:597

cv::blur
void blur(InputArray src, OutputArray dst, Size ksize, Point anchor=Point(-1,-1), int borderType=BORDER_DEFAULT)
Blurs an image using the normalized box filter.

cv::cvtColor
void cvtColor(InputArray src, OutputArray dst, int code, int dstCn=0)
Converts an image from one color space to another.

highgui.hpp

cv::imread
Mat imread(const String &filename, int flags=IMREAD_COLOR)
Loads an image from a file.

cv::Mat::zeros
static MatExpr zeros(int rows, int cols, int type)
Returns a zero array of the specified size and type.

cv::imshow
void imshow(const String &winname, InputArray mat)
Displays an image in the specified window.

imgcodecs.hpp

cv::drawContours
void drawContours(InputOutputArray image, InputArrayOfArrays contours, int contourIdx, const Scalar &color, int thickness=1, int lineType=LINE_8, InputArray hierarchy=noArray(), int maxLevel=INT_MAX, Point offset=Point())
Draws contours outlines or filled contours.

cv::createTrackbar
int createTrackbar(const String &trackbarname, const String &winname, int *value, int count, TrackbarCallback onChange=0, void *userdata=0)
Creates a trackbar and attaches it to the specified window.

cv::RETR_TREE
Definition: imgproc.hpp:409

cv::contourArea
double contourArea(InputArray contour, bool oriented=false)
Calculates a contour area.

cv::Point2f
Point_< float > Point2f
Definition: types.hpp:179

imgproc.hpp

cv::Mat::size
MatSize size
Definition: mat.hpp:1882

cv::arcLength
double arcLength(InputArray curve, bool closed)
Calculates a contour perimeter or a curve length.

cv::namedWindow
void namedWindow(const String &winname, int flags=WINDOW_AUTOSIZE)
Creates a window.

cv::Canny
void Canny(InputArray image, OutputArray edges, double threshold1, double threshold2, int apertureSize=3, bool L2gradient=false)
Finds edges in an image using the Canny algorithm .

cv::Size
Size2i Size
Definition: types.hpp:308

i
for i
Definition: modelConvert.m:63

cv::RNG
Random Number Generator.
Definition: core.hpp:2600

CV_8UC3
#define CV_8UC3
Definition: cvdef.h:118

cv::CHAIN_APPROX_SIMPLE
Definition: imgproc.hpp:421

cv::WINDOW_AUTOSIZE
Definition: highgui.hpp:138

cv::moments
Moments moments(InputArray array, bool binaryImage=false)
Calculates all of the moments up to the third order of a polygon or rasterized shape.

cv::findContours
void findContours(InputOutputArray image, OutputArrayOfArrays contours, OutputArray hierarchy, int mode, int method, Point offset=Point())
Finds contours in a binary image.

main
int main(int argc, const char *argv[])
Definition: facerec_demo.cpp:67

cv::Scalar_< double >

cv::Mat
n-dimensional dense array class
Definition: mat.hpp:726

cv::circle
void circle(InputOutputArray img, Point center, int radius, const Scalar &color, int thickness=1, int lineType=LINE_8, int shift=0)
Draws a circle.

cv::Point
Point2i Point
Definition: types.hpp:181

cv::COLOR_BGR2GRAY
convert between RGB/BGR and grayscale, color conversions
Definition: imgproc.hpp:511

cv::waitKey
int waitKey(int delay=0)
Waits for a pressed key.