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How to tag persons in an image in OpenCV?

asked 2014-10-26 21:42:31 -0500

Sowmya gravatar image

I am working on the problem of face recognition. I need a help to display, the name of that person in the image by tagging(Display the name of the person by performing face recognition). Can anyone help me with this?

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answered 2014-10-27 05:04:50 -0500

updated 2014-10-27 05:05:26 -0500

Hi, I would decompose the problem in two steps : create a learning database of the person you want to tag, and the recognition step. For the first step, you will first have to create a database containing multiple view of the face of each person you want to recognize. That database will consist of a list of pictures with the corresponding name. So to sum up:

vector<Mat> images;
vector<int> labels;
vector<string> names;
images = [pic1;pic2;pic3;pic4;...]
labels = [0   ;0   ;1   ;2   ;...]
names  = [nom1;nom2;nom3]

In this example, you have 3 persons, with some pictures of them. labels correspond to the index in the names vector.

You can then use a classifier (I suggest you the LBP face detector):

Ptr<FaceRecognizer> model =  createLBPHFaceRecognizer();
model->train(images, labels);

Now model contains everything you need to tag peoples. To get the class, you just have to do that:

int predicted = model->predict(askingImg);
cout<<"Hello "<<names[predicted]<<"!"<<endl;
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Thanks for your suggestion. I tried the following code for face recognition in videos And I made necessary changes according to your answer to display names in the program. But I failed to do it. When I say this int predicted = model->predict(askingImg); cout<<names[prediction]<<endl; nothing is displayed in the command window.

Please let me know if there is a way to tag people in a video.

Sowmya gravatar imageSowmya ( 2014-11-14 03:07:57 -0500 )edit

answered 2014-11-14 03:01:28 -0500

Sowmya gravatar image

I actually tried with your answer. But the name of the person is not getting displayed in the video. I am now trying to display names of person in a video. For that I am using the code from the following link

and I tried your answer to display the names of the persons in the video. But it is failing. Below is the code //g++ -ggdb pkg-config --cflags opencv -o basename online_faceRec_video.cpp .cpp online_faceRec_video.cpp pkg-config --libs opencv

/* * Copyright (c) 2011. Philipp Wagner <bytefish[at]gmx[dot]de>. * Released to public domain under terms of the BSD Simplified license.

  • Redistribution and use in source and binary forms, with or without
  • modification, are permitted provided that the following conditions are met:
    • Redistributions of source code must retain the above copyright
  • notice, this list of conditions and the following disclaimer.
    • Redistributions in binary form must reproduce the above copyright
  • notice, this list of conditions and the following disclaimer in the
  • documentation and/or other materials provided with the distribution.
    • Neither the name of the organization nor the names of its contributors
  • may be used to endorse or promote products derived from this software
  • without specific prior written permission.

include "/usr/local/include/opencv2/core/core.hpp"

include "/usr/local/include/opencv2/contrib/contrib.hpp"

include "/usr/local/include/opencv2/highgui/highgui.hpp"

include "/usr/local/include/opencv2/imgproc/imgproc.hpp"

include "/usr/local/include/opencv2/objdetect/objdetect.hpp"

include <iostream>

include <fstream>

include <sstream>

using namespace cv; //using namespace cv::face; using namespace std;

static void read_csv(const string& filename, vector<mat>& images, vector<int>& labels, vector<string>& names, char separator = ';') { std::ifstream file(filename.c_str(), ifstream::in); if (!file) { string error_message = "No valid input file was given, please check the given filename."; CV_Error(CV_StsBadArg, error_message); } string line, path, classlabel,classnames; while (getline(file, line)) { stringstream liness(line); getline(liness, path, separator); getline(liness, classlabel); getline(liness, classnames); if(!path.empty() && !classlabel.empty()) { images.push_back(imread(path, 0)); labels.push_back(atoi(classlabel.c_str())); names.push_back(classnames.c_str()); } } } int main(int argc, const char *argv[]) { // Check for valid command line arguments, print usage // if no arguments were given. if (argc != 4) { cout << "usage: " << argv[0] << " </path> </path> </path>" << endl; cout << "\t </path> -- Path to the Haar Cascade for face detection." << endl; cout << "\t </path> -- Path to the CSV file with the face database." << endl; cout << "\t <device id=""> -- The webcam device id to grab frames from." << endl; exit(1); } // Get the path to your CSV: string fn_haar = string(argv[1]); string fn_csv = string(argv[2]); int deviceId = atoi(argv[3]); // These vectors hold the images and corresponding labels: vector<mat> images; vector<int> labels; vector<string> names;

try {
    read_csv(fn_csv, images, labels,names);
} catch (cv::Exception& e) {
    cerr << "Error opening file \"" << fn_csv << "\". Reason: " << e.msg << endl;        

int im_width = images[0].cols;
int im_height = images[0].rows;
Ptr<FaceRecognizer> model = createFisherFaceRecognizer ...
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Asked: 2014-10-26 21:42:31 -0500

Seen: 1,651 times

Last updated: Nov 14 '14