C++ OPENCV 4.3.0 x64 Why face_cascade throws error? - c++

Question

I am using OpenCV to add a face recognition feature to my C++ program. I have never used it before and I cant seem to get the cascade feature for facial recognition to work. I am wondering if they have made some changes for the FLAGS in the new version. I can display an image but when that comes to the cascade it always throws an error. Can anyone tell me what am I missing?
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc.hpp>
#include <stdio.h>
#include <iostream>
#include <opencv2\objdetect.hpp>
using namespace std;
using namespace cv;
String face_cascade_name = "sources/data/haarcascades/haarcascade_frontalface_default.xml";
String eyes_cascade_name = "sources/data/haarcascades/haarcascade_eye_tree_eyeglasses.xml";
String smile_cascade_name = "sources/data/haarcascades/haarcascade_smile.xml";
CascadeClassifier face_cascade;
CascadeClassifier eyes_cascade;
CascadeClassifier smile_cascade;
string window_name = "Capture - Face detection";
RNG rng(12345);
int main()
{
//-- 1. Load the cascades
if (!face_cascade.load(face_cascade_name)) { printf("--(!)Error loading file 1\n"); return -1; };
if (!eyes_cascade.load(eyes_cascade_name)) { printf("--(!)Error loading file 2\n"); return -1; };
if (!smile_cascade.load(smile_cascade_name)) { printf("--(!)Error loading file 3\n"); return -1; };
std::string image_path = samples::findFile("test.jpg");
Mat img = imread(image_path, IMREAD_COLOR);
Mat img_gry;
if (img.empty())
{
std::cout << "Could not read the image: " << image_path << std::endl;
return 1;
}
imshow("Display window", img);
// Detect faces
std::vector<Rect> faces;
cvtColor(img, img_gry, COLOR_BGR2GRAY);
equalizeHist(img, img_gry);
//I GET ERROR HERE
face_cascade.detectMultiScale(img_gry, faces, 1.1, 2, CASCADE_SCALE_IMAGE, Size(30, 30), Size(130, 130)); //I GET ERROR HERE
/*...REST WILL BE PARSING faces...*/
int g_key = waitKey(0); // Wait for a keystroke in the window
if (g_key == 's')
{
imwrite("starry_night.png", img); //save image in same path
}
return 0;
}

Answer 1

I modified the code as:
/*...
OTHER CODE
...*/
std::vector<Rect> faces;
cvtColor(img, img_gry, COLOR_BGR2GRAY);
equalizeHist(img_gry, img_gry);
face_cascade.detectMultiScale(img_gry, faces);
for (size_t i = 0; i < faces.size(); i++)
{
/*...PARSE...*/
}
imshow("Display window", img);
As #SourceCode mentioned :
equalizeHist( smallImg, smallImg); //my variable is img_gry instead.
But also, I modified :
face_cascade.detectMultiScale(img_gry, faces, 1.1, 2, CASCADE_SCALE_IMAGE, Size(30, 30), Size(130, 130));
To
face_cascade.detectMultiScale(img_gry, faces);
Otherwise it does not work in my case.
Source if that helps: https://docs.opencv.org/3.4/db/d28/tutorial_cascade_classifier.html

Answer 2

Have you tried using something like:
face_cascade.detectMultiScale(img_gry, faces, 1.1, 2, 0|CASCADE_SCALE_IMAGE, Size(30, 30));