Fast Opencv people pedestrian detection Tutorial


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    Simple Opencv C++ tutorial and example of people detection in video samples and pictures. There is nothing you cannot achieve in few simple steps. People detection and performace tasks in opencv could be solved if you have little bit knowledge of programing. Or just simple follow the steps.. 

    Opencv tutorial instalation of opencv

    You can simple prepare the project inside the Visual Studio 2015 by Nuget Packages. This approach is easy for beginers and better than standard installation with all the environmental variables problems. Just follow the installation steps inside here 

    Cascade Classifier detect Multi Scale

    Opencv is great and complex tools. There is lot of image processing and also machine learning features. You can simply learn your own detector. I would like to prepare some tutorial how to learn your own detector. It is long time run. 

    All, you need to do, is some experience and basic opencv tools. 
    under opencv/build/x64/vc14/bin


    Prepare your dataset and files with labels are better under linux. You can use simple shall scripts. 
    This is really for long tutorial, but you can do image annotation in windows as well and maybe use the new tool opencv_annotation,exe, but i dont have any experience with this. My own scripts and programs crop, saves and annotating data. I have own image cropper to prepare datasets. You can build your own dataset in few days. It is tricky to. 

    First step

    Use basic opencv cascades to crop some positive samples from video or better crop precisely the positive samples from your images. Negative samples is not problem. Generate them randomly from your images.  Clean and prepare data manually.. This is a worse part. Crop also images selected correctly by default opencv cascade to achieve better results.

    Second step

    Build your initial detector, which is used for another positive data collecting.  Again Clean and prepare data manually. Stupid boring and it takes a long time.


    !!Use this on your own risk. !!

    Run cloud machine on aws and install opencv 3.1. 
    Better is memory than number of cores.. Something like 

    r3.4xlarge   cores 16  memory 52                              $1.33 per Hour

     !!!!On your own risk!!!!

    8000 positive and 15000 negatives dataset with 10- 20 stages could take minutes - hours instead of days of learning on your own computer.. And it's cheaper than electricity bill.Time to learn depends on number of data, parameters, selected machine and many things.I can not guarantee that it goes so fast with your data and parameters.. I do it this way saves time. I am preaty sure that your first detector will be terrible. In the cloud you can learn 10 detectors day. Which is great

    Performance detectMultiScale and parameters

    • Source image is 640x480 image. My PC is notebook I7, 4 cores, 8 threads and huge amount of RAM :). Opencv version is 3.1 default for windows machines. 

    • I have 2 people detector detectMultiScale in the main loop . 

    • The main performance issue is in scaleFactor parameter and minSize of the object. In faster case, I have 1.1 and in slower case is 1.02 scaleFactor.  

    • Choose appropriately as needed the minSize parameter. If you have to small window, your program need to check far more options. Size(40,70)

    CascadeClassifier at approximately 13 FPS

    detectorBody.detectMultiScale(img, human, 1.1, 1, 0 | 1, Size(40,70), Size(80, 300));
    detectorUpper.detectMultiScale(img, upperBody, 1.1, 1, 0 | 1, Size(40, 70), Size(80, 300));

    Cascade Classifier detect Multi Scale

    CascadeClassifier at approximately 2 FPS

    detectorBody.detectMultiScale(img, human, 1.02, 2, 0 | 1, Size(40,70), Size(80, 300));
    detectorUpper.detectMultiScale(img, upperBody, 1.02, 2, 0 | 1, Size(40, 70), Size(80, 300));

    Cascade Classifier detect Multi Scale

    Opencv  HAAR LBP cascade download

    I also learn some mine cascade on my own datasets. There are here. To be sure that you can reach them here are the links.. 

    Cascade for car detector download

    This is just basic 5 stage haar cascade car detector, post where to find my cascade to detect cars

    Cascade for head and people download 

    This cascade is also able to use by tutorial code below. For head and for people detection. 
    Learned by me on my own data set. cascade for head and people detection

    Opencv CascadeClassifier tutorial code

    !!Simple as opencv Sample.. Let me add some useful remarks. Some windows opencv version of detect multiScale return errors.. 2.9.4 -3.0 maybe 3.1. I don't know why. The classifier returns to many output rectangles out of bound. This does not make sense and kill your program.. 
    If this is a issue of your error on windows.. Switch from debug to release. It helps. !! Really

    #include "opencv2\highgui.hpp"
    #include "opencv2\imgproc.hpp"
    #include "opencv2\objdetect\objdetect.hpp"
    #include "opencv2/video/tracking.hpp"
    #include <vector>
    #include <stdio.h>
    #include <Windows.h>
    #include <iostream>
    #include <time.h>
    #include <ctime>

    using namespace cv;
    using namespace std;

    int main(int argc, const char** argv)

             // prepare video input
    VideoCapture cap("");
             // prepare video output
    VideoWriter outputVideo;"video4.wmv", CV_FOURCC('W', 'M', 'V', '2'), cap.get(CV_CAP_PROP_FPS), Size(640, 480), true);

            // prepare cascadeClassifier
    CascadeClassifier detectorBody;
    CascadeClassifier detectorUpper;
    // !! Put your cascade or opencv cascede into project folder !!
    string cascadeName1 = "cascadeName.xml";
    string cascadeName2 = "cascadeName.xml";

            // Load cascade into CascadeClassifier
    bool loaded1 = detectorBody.load(cascadeName1);
    bool loaded3 = detectorUpper.load(cascadeName2);

      // Basic video input loop
    for (;;)

    bool Is = cap.grab();
    if (Is == false) {

    cout << "Video Capture Fail" << endl;
    else {
    // Just for measure time
    const clock_t begin_time = clock();

                            // Store results in these 2 vectors
    vector<Rect> human;
    vector<Rect> upperBody;

                            // prepare 2 Mat container
    Mat img;
    Mat original;

    // capture frame from video file
    cap.retrieve(img, CV_CAP_OPENNI_BGR_IMAGE);
    // Resize image if you want with same size as your VideoWriter
    resize(img, img, Size(640, 480));
                            // Store original colored image
                            // color to gray image
    cvtColor(img, img, CV_BGR2GRAY);

    // detect people, more remarks in performace section
    detectorBody.detectMultiScale(img, human, 1.1, 2, 0 | 1, Size(40,70), Size(80, 300));
    detectorUpper.detectMultiScale(img, upperBody, 1.1, 2, 0 | 1, Size(40, 70), Size(80, 300));

                            // Draw results from detectorBody into original colored image
    if (human.size() > 0) {
    for (int gg = 0; gg < human.size(); gg++) {

    rectangle(original, human[gg].tl(), human[gg].br(), Scalar(0,0,255), 2, 8, 0);


                           // Draw results from detectorUpper into original colored image
    if (upperBody.size() > 0) {
    for (int gg = 0; gg < upperBody.size(); gg++) {

             rectangle(original, upperBody[gg].tl(), upperBody[gg].br(),  Scalar(255,0,0), 2, 8, 0);

    // measure time as current - begin_time
           clock_t diff = clock() - begin_time;
                                    // convert time into string
           char buffer[126];
           sprintf(buffer, "%d",diff);
    // display TIME ms on original image
            putText(original, buffer, Point(100, 20), 1, 2, Scalar(255, 255, 255), 2, 8, 0);
            putText(original, "ms" , Point(150, 20), 1, 2, Scalar(255, 255, 255), 2, 8, 0);
                                    // draw results
    namedWindow("prew", WINDOW_AUTOSIZE);
    imshow("prew", original);
                                    // make video output
    outputVideo << original; 

    int key1 = waitKey(20);



    1. I will try this code on my own. Hope it will help me.

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    2. Awesome! Thanks for sharing code!!

    3. Hi. I am referening this tutorial. Could you give me this code? I want to reference it. Thanks a lot. My email:

    4. This comment has been removed by the author.

    5. Hi! What an interesting blog!!
      I'm working on a ROS module for person detection and I was wondering if you could give me the CascadeClassifier(body detector) you used because I couldn't find the link in this tutorial.
      Thanks for your help!
      My email:

    6. Hi,
      Very good example and useful for some use cases. It is possible to send the code? My email:
      Thanks and good work