Odd Shape Object tracking with opencv and C++

[waduwan4]

Hi,

Currently I have a program to detect odd shape object from web cam. The program is able to draw a contour line around the objects. Now I need to calculate the area of the objects(contours) and display it on Labview. By the way, is it possible for me to display the "area" on Labview?

I know I can use cvContourArea() to get the area. But I do not know what to input in the brackets and where should I use it in my program.

If possible, can also teach me how to display the area in units like mm or cm ?

Thank you very much.

Below is my current program.

#include "stdafx.h"
#include <iostream>
#include <cv.h> //main OpenCV functions
#include <highgui.h> //OpenCV GUI functions¯include <stdio.h>

using namespace std;

CvCapture* capture = 0; //image window
IplImage *img = 0;
IplImage *gray;

int main()
{
CvCapture* capture = cvCaptureFromCAM(0); //Initializing camera
IplImage *img1 = cvRetrieveFrame(capture); //Capture a frame and retrieve the frame

IplImage * original = cvCreateImage(cvGetSize(img1),8,3); ;//cvCloneImage(img1); //cvLoadImage("image.jpg",1);
IplImage * img = cvCreateImage(cvGetSize(original),8,1); //cvLoadImage("image.jpg",0);
IplImage * bw = cvCreateImage(cvGetSize(original),8,1);
cvNamedWindow("Test");

while(1){
//Capturing the image
img1 = cvRetrieveFrame(capture);
//cvSaveImage("image.jpg",img1);

cvCopyImage(img1,original);


cvCvtColor(original,img,CV_RGB2GRAY);
// Find Egdes
cvCanny(img, bw,0,100);
cvShowImage("Test",bw);

// fill some holes in the contours (comment out those lines to see the difference)
cvDilate(bw, bw, NULL, 2);
cvErode(bw, bw, NULL, 2);

// Create Memory for contour-search
CvMemStorage* stor = cvCreateMemStorage(0);
CvSeq* cont = cvCreateSeq(CV_SEQ_ELTYPE_POINT, sizeof(CvSeq), sizeof(CvPoint) , stor);


// find external contours
cvFindContours( bw, stor, &cont, sizeof(CvContour), CV_RETR_EXTERNAL, 2, cvPoint(0,0));


// some fun with the color, ignore it (just some transformation of color-space)
cvCvtColor(original, original, CV_RGB2HSV);




// loop over all contours
for(;cont;cont = cont->h_next)
{
// size of pointArray and polygon
int point_cnt = cont->total;


cout << "point_cnt: " << point_cnt << endl;


// no small contours
if (point_cnt<20){
continue;
}


// Allocate memory for contour point set.
CvPoint* PointArray = (CvPoint*)malloc( point_cnt*sizeof(CvPoint) );


// Get contour point set.
cvCvtSeqToArray(cont, PointArray, CV_WHOLE_SEQ);



for (int i=0; i<=point_cnt; i++){
// Show the Pixelcoordinates
cout << PointArray[i].x << " " << PointArray[i].y << endl;


// have some fun with the color
int h_value = int(i*3.0/point_cnt*0)%100;

cvLine(original, PointArray[i%point_cnt], PointArray[(i+1)%point_cnt],cvScalar(h_value, 255, 255), 4 );
}



}




// back to RGB-colorSpace

cvCvtColor(original, original, CV_HSV2BGR);


cvNamedWindow("img", 1);
cvShowImage("img", original);

cvWaitKey(500);
if (cvWaitKey(500)==27)break;
}

cvReleaseImage(&original);
cvReleaseImage(&img);
cvReleaseImage(&bw);
cvDestroyAllWindows();
return 0;
}