Can someone explain about detectMultiScale in openCV - c++

Question

I've been trying objectDetection in openCV..
Followed a few steps..
Resizing it to 64x64 resolution
Changing it to gray scale
Fetching XML for object detection
Drawing rectangle fringing the pattern
Yet, I couldn't achieve it..
Here's my code :
#include<iostream>
#include "cv.h"
#include "highgui.h"
#include<vector>
using namespace cv;
using namespace std;
int main()
{
IplImage* img;
img = cvLoadImage( "hindi3.jpg" );
vector<cv::Rect> objects;
// ***Resize image to 64x64 resolution***
IplImage *resizeImage = cvCreateImage(cvSize(64,64),8,3);
cvResize(img,resizeImage,CV_INTER_LINEAR);
cvShowImage("Resize",resizeImage);
cvWaitKey(0);
// ***Convert image to grayscale***
IplImage *grayImage = cvCreateImage(cvGetSize(resizeImage),8,1);
cvCvtColor(resizeImage,grayImage,CV_BGR2GRAY);
cvShowImage("gray",grayImage);
cvWaitKey(0);
// ***Getting the XML (Cascade xml generated thru haarTraining)***
CvMemStorage* storage = cvCreateMemStorage(0);
cout<<"Memory created\n";
cv::CascadeClassifier cascade;
cascade.load("cascade.xml");
//CvHaarClassifierCascade* cascade = (CvHaarClassifierCascade*)cvLoad( "cascade.xml" );
cout<<"cascade.xml loaded successfully\n";
double scale = 1.3;
static CvScalar colors[] = { {{0,0,255}}, {{0,128,255}}, {{0,255,255}},
{{0,255,0}}, {{255,128,0}}, {{255,255,0}}, {{255,0,0}}, {{255,0,255}} };
// ***Detect objects***
cvClearMemStorage( storage );
objects.clear();
//CvSeq* objects = cvHaarDetectObjects( grayImage, cascade, storage, 1.1, 4, 0, cvSize( 40, 50 ));
//cascade.detectMultiScale(grayImage, objects, 1.2, 4, CV_HAAR_DO_CANNY_PRUNING, cvSize(30, 30));
cascade.detectMultiScale(grayImage, objects, 1.2, 4, CV_HAAR_SCALE_IMAGE, cvSize(30, 30));
// ***Draw a rectangle outside recognized pattern***
cout<<"Object size : "<<objects.size();
for( vector<cv::Rect>::const_iterator r = objects.begin(); r != objects.end(); r++)
{ //rectangle(img, *r, Scalar(0,0,255), 2, 8, 0);
cvRectangle( grayImage, cvPoint( r->x, r->y ), cvPoint( r->x + r->width, r->y + r->height ),Scalar(0,0,255));
cout<<"In the loop\n";
}
cvNamedWindow( "Output" );
cvShowImage( "Output", grayImage );
cvWaitKey(0);
cvReleaseImage(&resizeImage);
cvReleaseImage(&grayImage);
cvReleaseImage( &img );
return 0;
}
The object size printed by me shows 0 unfortunately :( Hence, it doesn't go to the for loop.. Can anyone help me out..
Thanks in advance
PS : I've commented some lines in the code which were not useful. Please lemme know if I can incorporate the same.

Answer 1

Found the answer..! I've missed out the specified arguments for detectMultiScale function.
It's working fine..Rectified code as follows
#include<iostream>
#include "cv.h"
#include "highgui.h"
#include<vector>
using namespace cv;
using namespace std;
int main()
{
IplImage* img;
img = cvLoadImage( "test.jpg" );
vector<cv::Rect> objects;
/*** Resizing is optional***
*****************************
IplImage *resizeImage = cvCreateImage(cvSize(64,64),8,3);
cvResize(img,resizeImage,CV_INTER_LINEAR);
cvShowImage("Resize",resizeImage);
cvWaitKey(0);*/
/*** Change image into grayscale***
**********************************/
IplImage *grayImage = cvCreateImage(cvGetSize(img),8,1);
cvCvtColor(img,grayImage,CV_BGR2GRAY);
//cvEqualizeHist(grayImage,grayImage); This is optional
cvShowImage("gray",grayImage);
cvWaitKey(0);
CvMemStorage* storage = cvCreateMemStorage(0);
cout<<"Memory created\n";
/*** Load the XML generated through haartraining***
**************************************************/
cv::CascadeClassifier cascade;
cascade.load("cascade.xml");
//CvHaarClassifierCascade* cascade = (CvHaarClassifierCascade*)cvLoad( "cascade.xml" );
cout<<"cascade.xml loaded successfully\n";
double scale = 1.3;
static CvScalar colors[] = { {{0,0,255}}, {{0,128,255}}, {{0,255,255}},
{{0,255,0}}, {{255,128,0}}, {{255,255,0}}, {{255,0,0}}, {{255,0,255}} };
/*** Detect objects***
**********************/
cvClearMemStorage( storage );
objects.clear();
//CvSeq* objects = cvHaarDetectObjects( grayImage, cascade, storage, 1.1, 4, 0, cvSize( 40, 50 ));
//cascade.detectMultiScale(grayImage, objects, 1.2, 4, CV_HAAR_DO_CANNY_PRUNING, cvSize(30, 30)); if captured through WebCam
cascade.detectMultiScale(grayImage, objects, 1.1, 3, CV_HAAR_SCALE_IMAGE | CV_HAAR_DO_CANNY_PRUNING,cvSize(0,0), cvSize(100,100));
cout<<"Object size : "<<objects.size();
/***Draw Rectangle outside recognized pattern***
***********************************************/
for( vector<cv::Rect>::const_iterator r = objects.begin(); r != objects.end(); r++)
{ //rectangle(img, *r, Scalar(0,0,255), 2, 8, 0);
cvRectangle( grayImage, cvPoint( r->x, r->y ), cvPoint( r->x + r->width, r->y + r->height ),Scalar(0,0,255));
cout<<"In the loop\n";
}
cvNamedWindow( "Output" );
cvShowImage( "Output", grayImage );
cvWaitKey(0);
//cvReleaseImage(&resizeImage); If resized
cvReleaseImage(&grayImage);
cvReleaseImage( &img );
return 0;
}
And finally this worked..!
PS: This program holds good only when the input is taken through image unlike WebCam or Video.