opencv-face detection-save the video - opencv

Question

I have code for detection of a face.. How do I save the video which is being captured? I'm posting the code for face detection below..
where do I insert the code which saves the the video?
thhis code works in detecting a face with ubuntu and opencv. Please do help!
#include <opencv2/objdetect/objdetect.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>
#include <stdio.h>
using namespace std;
using namespace cv;
VideoCapture cap;
cv::VideoWriter output_cap("/home/unifyadmin/Documents/MyVideo.avi",
input_cap.get(CV_CAP_PROP_FOURCC),
input_cap.get(CV_CAP_PROP_FPS),
cv::Size(input_cap.get(CV_CAP_PROP_FRAME_WIDTH),
input_cap.get(CV_CAP_PROP_FRAME_HEIGHT)));
if (!output_cap.isOpened())
{
std::cout << "!!! Output video could not be opened" << std::endl;
return;
}
// This part would be similar to your imshow part of your code
while (true)
{
if (!input_cap.read(frame))
break;
output_cap.write(frame);
}
/** Function Headers */
void detectAndDisplay( Mat frame );
/** Global variables */
String face_cascade_name = "haarcascade_frontalface_alt.xml";
String eyes_cascade_name = "haarcascade_eye_tree_eyeglasses.xml";
CascadeClassifier face_cascade;
CascadeClassifier eyes_cascade;
string window_name = "Capture - Face detection";
RNG rng(12345);
/** #function main */
int main( int argc, const char** argv )
{
CvCapture* capture;
Mat frame;
//-- 1. Load the cascades
if( !face_cascade.load( face_cascade_name ) ){ printf("--(!)Error loading\n"); return -1; };
if( !eyes_cascade.load( eyes_cascade_name ) ){ printf("--(!)Error loading\n"); return -1; };
//-- 2. Read the video stream
capture = cvCaptureFromCAM( 0 );
if( capture )
{
while( true )
{
frame = cvQueryFrame( capture );
//-- 3. Apply the classifier to the frame
if( !frame.empty() )
{ detectAndDisplay( frame ); }
else
{ printf(" --(!) No captured frame -- Break!"); break; }
int c = waitKey(10);
if( (char)c == 'c' ) { break; }
}
}
return 0;
}
/** #function detectAndDisplay */
void detectAndDisplay( Mat frame )
{
std::vector<Rect> faces;
Mat frame_gray;
cvtColor( frame, frame_gray, CV_BGR2GRAY );
equalizeHist( frame_gray, frame_gray );
//-- Detect faces
face_cascade.detectMultiScale( frame_gray, faces, 1.1, 2, 0|CV_HAAR_SCALE_IMAGE, Size(30, 30) );
for( size_t i = 0; i < faces.size(); i++ )
{
Point center( faces[i].x + faces[i].width*0.5, faces[i].y + faces[i].height*0.5 );
ellipse( frame, center, Size( faces[i].width*0.5, faces[i].height*0.5), 0, 0, 360, Scalar( 255, 0, 255 ), 4, 8, 0 );
Mat faceROI = frame_gray( faces[i] );
std::vector<Rect> eyes;
//-- In each face, detect eyes
eyes_cascade.detectMultiScale( faceROI, eyes, 1.1, 2, 0 |CV_HAAR_SCALE_IMAGE, Size(30, 30) );
for( size_t j = 0; j < eyes.size(); j++ )
{
Point center( faces[i].x + eyes[j].x + eyes[j].width*0.5, faces[i].y + eyes[j].y + eyes[j].height*0.5 );
int radius = cvRound( (eyes[j].width + eyes[j].height)*0.25 );
circle( frame, center, radius, Scalar( 255, 0, 0 ), 4, 8, 0 );
}
}
//-- Show what you got
imshow( window_name, frame );
}

Answer 1

There are three library methods that you require:
VideoWriter::VideoWriter(const string& filename, int fourcc, double fps, Size frameSize, bool isColor=true)
VideoWriter::open(const string& filename, int fourcc, double fps, Size frameSize, bool isColor=true)
void VideoWriter::write(const Mat& image)
Here is a short example on how to use them:
// Do this near the start of your code
cv::VideoWriter output_cap(C:/MyVideo.avi,
input_cap.get(CV_CAP_PROP_FOURCC),
input_cap.get(CV_CAP_PROP_FPS),
cv::Size(input_cap.get(CV_CAP_PROP_FRAME_WIDTH),
input_cap.get(CV_CAP_PROP_FRAME_HEIGHT)));
if (!output_cap.isOpened())
{
std::cout << "!!! Output video could not be opened" << std::endl;
return;
}
// This part would be similar to your imshow part of your code
while (true)
{
if (!input_cap.read(frame))
break;
output_cap.write(frame);
}
Edit: - My last contribution to this question:
You need your creation of objects into the main function, that includes the VideoWriter
Im not sure how any of this code even works:
VideoCapture cap;
cv::VideoWriter output_cap("/home/unifyadmin/Documents/MyVideo.avi",
input_cap.get(CV_CAP_PROP_FOURCC),
input_cap.get(CV_CAP_PROP_FPS),
cv::Size(input_cap.get(CV_CAP_PROP_FRAME_WIDTH),
input_cap.get(CV_CAP_PROP_FRAME_HEIGHT)));
if (!output_cap.isOpened())
{
std::cout << "!!! Output video could not be opened" << std::endl;
return;
}
// This part would be similar to your imshow part of your code
while (true)
{
if (!input_cap.read(frame))
break;
output_cap.write(frame);
}
You need to think about what you are actually coding and where you are writing code. Don't just take examples from the internet and try and stick them together.