Argthtjtr

The picture linked below shows the specific exception I'm getting. I'm not quite sure why I'm having this particular issue as I've built everything in the same directory, so the library file is there. From what I understand this has something to do with what I'm returning to my main method from my c++ function.

What I'm essentially trying to do is pass the name (printId) of the recognized person, as a string, from my c++ function to java.

Picture of command line:

Here's my C++ code:

#include <jni.h>

#include <iostream>

#include "opencv2/highgui/highgui.hpp"

#include "opencv2/imgproc/imgproc.hpp"

#include "opencv2/core/core.hpp"

#include "opencv2/opencv.hpp"

#include "opencv2/objdetect.hpp"

#include "opencv2/face.hpp"

#include "opencv2/face/facerec.hpp"

#include <vector>

#include <string>

#include "recognitionJNI.h"



#include <fstream>

#include <sstream>



using namespace cv;

using namespace std;





String face_cascade_name = "/Users/greg/Downloads/opencv-3.4.2/data/haarcascades/haarcascade_frontalface_alt.xml";

CascadeClassifier face_cascade;

String fn_csv = "/Users/greg/Desktop/faceBuild/faceRecognition/faceRecognition/csv.txt";



//User Defined Function for reading csv

static void read_csv(const string& filename, vector<Mat>& images, vector<int>& labels, char separator = ';') {



ifstream file(filename.c_str(), ifstream::in); //opens file for reading

if(!file) {

    cout << "ERROR: There was a problem loading the csv file" << endl;

}



string line, path, classlabel;

while(getline(file,line)) {

    stringstream liness(line);

    getline(liness, path, separator); //read stream object up to the semicolon

    getline(liness, classlabel);      //read the rest of stream object up to null terminated character



    //make sure that the filepath and userID are not empty

    if(!path.empty() && !classlabel.empty()) {

        images.push_back(imread(path,0)); //appends grayscale image to images vector

        labels.push_back(atoi(classlabel.c_str())); //appends userID to labels vector

      }



   }



}



JNIEXPORT jstring JNICALL Java_testJNIString_userName(JNIEnv *env, jobject thisObj, jstring inJNIStr) {



const char *inCStr = env->GetStringUTFChars(inJNIStr, NULL);

if (NULL == inCStr) return NULL;

string outCppStr;



cout << "In C++, the received string is: " << inCStr << endl;

env->ReleaseStringUTFChars(inJNIStr, inCStr);



string printId;

vector<Mat> images; //This vector will hold the images

vector<int> labels; //This vector will hold the userID



//read the csv file contain image paths and userID's

try {

    read_csv(fn_csv, images, labels);

} catch (Exception& e) {

    cerr << "Error opening file"" << fn_csv << "". Reason: " << e.msg << endl;

    exit(1);

}

//we'll need to resize the images to their origal size

//These two lines capture the length and width of the mat object

int im_width = images[0].cols;

int im_height = images[0].rows;



for(int j=0; j < images.size(); j++) {

    resize(images[j],images[j],Size(im_width, im_height),1.0,1.0,INTER_CUBIC);

}



//int numComponents = 2;

//double threshold = 10.0;



//creats a faceRecognizer to train with given images

Ptr<cv::face::FisherFaceRecognizer> model = cv::face::FisherFaceRecognizer::create();

model->train(images, labels);



string camera_msg = "No camera found";



Mat webcam;             // creates Mat object for to store frames

VideoCapture cap(0);    // opens default webcam

if(!cap.isOpened()) {

    return env->NewStringUTF(camera_msg.c_str());

}



face_cascade.load(face_cascade_name); //loads xml file into classifier



//load capture device into Mat object

while (cap.read(webcam)) {





    vector<Rect> faces;

    Mat frame_gray; //will be used to store grayscale copy of webcam



    cvtColor(webcam, frame_gray, COLOR_BGR2GRAY); //coverts Mat object frames into grayscale

    equalizeHist(frame_gray, frame_gray);         //maps input distrubution to more uniform distribution





    //locate the faces in the frame

    face_cascade.detectMultiScale(frame_gray, faces, 1.1, 5, 0|CASCADE_SCALE_IMAGE,Size(30,30));



    for(size_t i=0; i < faces.size(); i++) {



        Rect face_i = faces[i]; //process faces by frame

        Mat face = frame_gray(face_i); //takes the face from the live images



        //resize faces for prediction

        Mat face_resized;

        resize(face,face_resized,Size(im_width, im_height),1.0,1.0,INTER_CUBIC);



        int prediction = model->predict(face_resized); //predict based on resize faces



        if(prediction == 1 ) {

            printId = "Matthew";

        }

        else if (prediction == 2) {

            printId = "Greg";

            return env->NewStringUTF(printId.c_str());



        }

        else if(prediction != 1 || 2 ){

            printId = "Unknown";

        }



        rectangle(webcam, face_i, CV_RGB(0,255,0), 1); //draws a rectangle around the face

        string box_text = "Prediction = " + printId;



        int pos_x = std::max(face_i.tl().x - 10, 0);

        int pos_y = std::max(face_i.tl().y - 10, 0);



        putText(webcam, box_text, Point(pos_x,pos_y), FONT_HERSHEY_PLAIN, 1.0, CV_RGB(0,255,0), 1);



    }



    imshow("Webcam", webcam);

    waitKey(1);

    destroyAllWindows();



  }



return env->NewStringUTF(printId.c_str());



}

Here's my Java code:

public class recognitionJNI{

    static {

    System.loadLibrary("recogjni");

}

    private native String userName(String msg);



    public static void main(String args) {

    String result = new recognitionJNI().userName("Pass arg from c++ function");

    System.out.println(result);

    }

}

Try regenerating the header file, it looks like you changed your class name in the meantime and the name is no longer up to date. The name I get from that java class is:

Java_recognitionJNI_userName

But you have

Java_testJNIString_userName