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I want to do a quick test on a classifier xml file for Banana named banana_classifier.xml provided here:
http://coding-robin.de/2013/07/22/train-your-own-opencv-haar-classifier.html

I tested this trained xml file in the sample code provided by OpenCV in the examples like this:

#include "opencv2/objdetect.hpp"
#include "opencv2/videoio.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"

#include <iostream>
#include <stdio.h>

using namespace std;
using namespace cv;

/** Function Headers */
void detectAndDisplay(Mat frame);

/** Global variables */
String banana_cascade_name = "banana_classifier.xml";
CascadeClassifier banana_cascade;
String window_name = "Capture - Face detection";

/** @function main */
int main(void)
{
    VideoCapture capture;
    Mat frame;

    //-- 1. Load the cascades
    if (!banana_cascade.load(banana_cascade_name)){ printf("--(!)Error loading face cascade\n"); return -1; };

    //-- 2. Read the video stream
    capture.open(0);
    if (!capture.isOpened()) { printf("--(!)Error opening video capture\n"); return -1; }

    while (capture.read(frame))
    {
        if (frame.empty())
        {
            printf(" --(!) No captured frame -- Break!");
            break;
        }

        //-- 3. Apply the classifier to the frame
        detectAndDisplay(frame);

        int c = waitKey(10);
        if ((char)c == 27) { break; } // escape
    }
    return 0;
}

/** @function detectAndDisplay */
void detectAndDisplay(Mat frame)
{
    std::vector<Rect> bananas;
    Mat frame_gray;

    //Conversion of frame to grayscale
    cvtColor(frame, frame_gray, COLOR_BGR2GRAY);
    //Contrast enhance(Spread out intensity distribution)
    equalizeHist(frame_gray, frame_gray);
    //-- Detect Banana
    banana_cascade.detectMultiScale(frame_gray, bananas, 1.1, 2, 0 | CASCADE_SCALE_IMAGE, Size(30, 30));
    cout << bananas.size();

    for (size_t i = 0; i < bananas.size(); i++)
    {
        Point center(bananas[i].x + bananas[i].width / 2, bananas[i].y + bananas[i].height / 2);
        ellipse(frame, center, Size(bananas[i].width / 2, bananas[i].height / 2), 0, 0, 360, Scalar(255, 0, 255), 4, 8, 0);


    }
    //-- Show what you got
    imshow(window_name, frame);
}

Above code works for fontal_face_default xml for face provided by OpenCV but the banana_classifier crashes the program. I was thinking that, perhaps the banana_classifier.xml was created with older version of OpenCV therefore using the older format inside the xml. So, I can either export the old format to new format(which is not possible I guess) or I could use the old code to test the old classifier.

Can anyone post a simple code for testing it in the old OpenCV? (Creating my own new trained classifier is gonna consume a lot of time which I don't have right now)

I am totally new to OpenCV. Please help me.