Undefined symbols for architecture x86_64: "_cvHaarDetectObjects" Eclipse - opencv

Question

I'm trying to build the following sample code:
#include "cv.h"
#include "highgui.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <math.h>
#include <float.h>
#include <limits.h>
#include <time.h>
#include <ctype.h>
// Create a string that contains the exact cascade name
const char* cascade_name = "/usr/share/src/OpenCV-2.3.1/data/haarcascades/haarcascade_frontalface_alt.xml";
// "C:/Program Files/OpenCV/data/haarcascades/haarcascade_frontalface_alt.xml";
/* "haarcascade_profileface.xml";*/
// Function prototype for detecting and drawing an object from an image
void detect_and_draw( IplImage* image );
// Main function, defines the entry point for the program.
int main( int argc, char** argv )
{
// Create a sample image
IplImage *img = cvLoadImage("1.pgm");
// Call the function to detect and draw the face positions
detect_and_draw(img);
// Wait for user input before quitting the program
cvWaitKey();
// Release the image
cvReleaseImage(&img);
// Destroy the window previously created with filename: "result"
cvDestroyWindow("result");
// return 0 to indicate successfull execution of the program
return 0;
}
// Function to detect and draw any faces that is present in an image
void detect_and_draw( IplImage* img )
{
// Create memory for calculations
static CvMemStorage* storage = 0;
// Create a new Haar classifier
static CvHaarClassifierCascade* cascade = 0;
int scale = 1;
// Create a new image based on the input image
IplImage* temp = cvCreateImage( cvSize(img->width/scale,img->height/scale), 8, 3 );
// Create two points to represent the face locations
CvPoint pt1, pt2;
int i;
// Load the HaarClassifierCascade
cascade = (CvHaarClassifierCascade*)cvLoad( cascade_name, 0, 0, 0 );
// Check whether the cascade has loaded successfully. Else report and error and quit
if( !cascade )
{
fprintf( stderr, "ERROR: Could not load classifier cascade\n" );
return;
}
// Allocate the memory storage
storage = cvCreateMemStorage(0);
// Create a new named window with title: result
cvNamedWindow( "result", 1 );
// Clear the memory storage which was used before
cvClearMemStorage( storage );
// Find whether the cascade is loaded, to find the faces. If yes, then:
if( cascade )
{
// There can be more than one face in an image. So create a growable sequence of faces.
// Detect the objects and store them in the sequence
CvSeq* faces = cvHaarDetectObjects( img, cascade, storage,
1.1, 2, CV_HAAR_DO_CANNY_PRUNING,
cvSize(40, 40) );
// Loop the number of faces found.
for( i = 0; i < (faces ? faces->total : 0); i++ )
{
// Create a new rectangle for drawing the face
CvRect* r = (CvRect*)cvGetSeqElem( faces, i );
// Find the dimensions of the face,and scale it if necessary
pt1.x = r->x*scale;
pt2.x = (r->x+r->width)*scale;
pt1.y = r->y*scale;
pt2.y = (r->y+r->height)*scale;
// Draw the rectangle in the input image
cvRectangle( img, pt1, pt2, CV_RGB(255,0,0), 3, 8, 0 );
}
}
// Show the image in the window named "result"
cvShowImage( "result", img );
// Release the temp image created.
cvReleaseImage( &temp );
}
And the path /usr/share/src....is the right path where the xml file is. I've linked the opencv libraries: opencv_core, opencv_imgproc, opencv_highgui and opencv_video to eclipse (and I think they are correctly linked since I build other opencv projects in this way). But Eclipse keeps throwing the following errors:
Invoking: MacOS X C++ Linker
g++ -L/usr/local/include/opencv -L/usr/local/include/opencv2 -L/usr/local/lib -o "OpenCVFace" ./main.o -lopencv_core -lopencv_highgui -lopencv_video -lopencv_imgproc
Undefined symbols for architecture x86_64:
"_cvHaarDetectObjects", referenced from:
detect_and_draw(_IplImage*) in main.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
make: *** [OpenCVFace] Error 1
**** Build Finished ****
I can see the cvHaarDetectObjects function is highlighted in Eclipse (which turned to purple color). Any ideas of how to solve the problem? Thanks!

Answer 1

You need to link to opencv_objdetect; include -lopencv_objdetect in the link flags.