The below is used to get the live video feed from the 4 webcam. But all the code i have written is limited only for four camera. I want to make this code dynamic that is. If two camera is connected it should only display two windows, if 3 are connected it should show 3 window. I am getting the number of camera attached to the System. I want to implement the code for that number of camera. Can someone please point me in right direction.
using namespace cv;
int main(){
//Create matrix to store image
Mat image;
Mat image1;
Mat image2;
Mat image3;
//Mat image1;
//initailize capture
videoInput VI;
int numDevices = VI.listDevices(); //getting number of camera attached to system dynamically.
VideoCapture cap;
VideoCapture cap1;
VideoCapture cap2;
VideoCapture cap3;
bool x = false;
//VideoCapture cap1;
cap.open(0);
cap1.open(1);
cap2.open(2);
cap3.open(3);
namedWindow("Camera 1",1);
namedWindow("Camera 2",1);
namedWindow("Camera 3",1);
namedWindow("Camera 4",1);
while(1){
//copy webcam stream to image
cap >> image;
cap1 >> image1;
cap2 >> image2;
cap3 >> image3;
cap4 >> image4;
//cap1 >> image1;
imshow("Camera 1",image);
imshow("Camera 2",image1);
imshow("Camera 3",image2);
imshow("Camera 4",image3);
//imshow("Camera 2",image1);
//delay 33ms
waitKey(33);
}
}
The link to a webcam is usually a direct http link. So, just create a static html file that has individual frame for each webcam link, arrange these frames the way that you want to view by using html code. Launch this static html page in your embedded browser of your application.
Related
I want to display a video read with OpenCV in a qt widget.I have already read the frames (have function that reads frames) but don't know how to show them. I need to show the video in a little widget in a window.
Please share a code that can help me.
as far as I know, you should play video in a Qlabel. this link might help you about Qlabel: https://doc.qt.io/qt-6/qlabel.html
at first create a label and then can play your video in while(1) loop; dont forgot that input shape of the image in Qlabel is QPixmap but shape of image in openCV is Mat; so you have to convet image shape from Mat to QPixmap.
for this you can convert mat to QImage and then you can convet QPixmap to QImage in Qt.
I hope you will realize it when you read code and its comments.
cv::VideoCapture cap("String Video Address");
if(!cap.isOpened())
QMessageBox::information(this, "", "error: Video not loaded "); // show error message
cv::Mat cvframe;
QImage Qframe;
while(1){
cap >> cvframe;
if (cvframe.empty())
break;
Qframe = convertOpenCVMatToQtQImage(cvframe);
ui->Video_lable->setPixmap(QPixmap::fromImage(Qframe)); // show images on form labels
ui->Video_lable->setScaledContents( true );
ui->Video_lable->setSizePolicy( QSizePolicy::Ignored, QSizePolicy::Ignored );
char c=(char)cv::waitKey(25); // waits to display frame
if(c==27)
break;
}
//The function that convert OpenCVMat To QtQImageQImage
QImage MainWindow::convertOpenCVMatToQtQImage(cv::Mat mat)
{
if(mat.channels() == 1) { // if 1 channel (grayscale or black and white) image
return QImage((uchar*)mat.data, mat.cols, mat.rows, mat.step, QImage::Format_Indexed8);// return QImage
}
else if(mat.channels() == 3) { // if 3 channel color image
cv::cvtColor(mat, mat, cv::COLOR_BGR2RGB);// flip colors
return QImage((uchar*)mat.data, mat.cols, mat.rows, mat.step, QImage::Format_RGB888);// return QImage
}
else {
qDebug() << "in convertOpenCVMatToQtQImage, image was not 1 channel or 3 channel, should never get here";
}
return QImage();// return a blank QImage if the above did not work
}
I am using new logitech camera c920 for my project to do object recognition .
My camera can support H264 codec and can display H264 HD output.
But How I can set CODEC type as H264 in my below code to get out put as H264 DECODED STREAM
by using OpenCV instruction .
I am capturing video by using below logic : ref:this link
#include "opencv2/opencv.hpp"
using namespace cv;
int main(int, char**)
{
VideoCapture cap(0); // open the default camera
if(!cap.isOpened()) // check if we succeeded
return -1;
for(;;)
{
Mat frame;
cap >> frame; // get a new frame from camera
imshow("display", frame);
if(waitKey(30) >= 0) break;
}
// the camera will be deinitialized automatically in VideoCapture destructor
return 0;
}
By setting the fourCC property, you should be telling VideoCapture that your source is h.264. All the docs for openCV say that you will get decoded BGR data out though.
cap.set(CV_CAP_PROP_FOURCC, CV_FOURCC('H', '2', '6', '4'));
I have an OpenCV application that displays a fullscreen window, via:
cv::namedWindow("myWindow", CV_WINDOW_NORMAL)
cv::setWindowProperties("myWindow", CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN)
It works fine, but when I have multiple monitors it always displays the fullscreen window on the First monitor. Is there any way to display on the 2nd monitor? I've tried setting X/Y and Width/Height, but they seem to be ignored once fullscreen is enabled.
Edits:
Sometimes pure OpenCV code cannot do a fullscreen window on a dual display. Here is a Qt way of doing it:
#include <QApplication>
#include <QDesktopWidget>
#include <QLabel>
#include <opencv2/highgui/highgui.hpp>
using namespace cv;
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QDesktopWidget dw;
QLabel myLabel;
// define dimension of the second display
int width_second = 2560;
int height_second = 1440;
// define OpenCV Mat
Mat img = Mat(Size(width_second, height_second), CV_8UC1);
// move the widget to the second display
QRect screenres = QApplication::desktop()->screenGeometry(1);
myLabel.move(QPoint(screenres.x(), screenres.y()));
// set full screen
myLabel.showFullScreen();
// set Qimg
QImage Qimg((unsigned char*)img.data, img.cols, img.rows, QImage::Format_Indexed8);
// set Qlabel
myLabel.setPixmap(QPixmap::fromImage(Qimg));
// show the image via Qt
myLabel.show();
return app.exec();
}
Don't forget to configure the .pro file as:
TEMPLATE = app
QT += widgets
TARGET = main
LIBS += -L/usr/local/lib -lopencv_core -lopencv_highgui
# Input
SOURCES += main.cpp
And in terminal compile your code as:
qmake
make
Original:
It is possible.
Here is a working demo code, to show a full-screen image on a second display. Hinted from How to display different windows in different monitors with OpenCV:
#include <opencv2/highgui/highgui.hpp>
using namespace cv;
int main ( int argc, char **argv )
{
// define dimension of the main display
int width_first = 1920;
int height_first = 1200;
// define dimension of the second display
int width_second = 2560;
int height_second = 1440;
// move the window to the second display
// (assuming the two displays are top aligned)
namedWindow("My Window", CV_WINDOW_NORMAL);
moveWindow("My Window", width_first, height_first);
setWindowProperty("My Window", CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);
// create target image
Mat img = Mat(Size(width_second, height_second), CV_8UC1);
// show the image
imshow("My Window", img);
waitKey(0);
return 0;
}
I've tried different ways to make it working, but unfortunetely it seems that this is not possible using OpenCV. The only thing you can do is probably display one window on main(primary) screen just using your current code and handle second window manually - set window position, resize image, and just use imshow function to display it. Here is some example:
void showWindowAlmostFullscreen(cv::Mat img, std::string windowTitle, cv::Size screenSize, cv::Point screenZeroPoint)
{
screenSize -= cv::Size(100, 100); //leave some place for window title bar etc
double xScallingFactor = (float)screenSize.width / (float)img.size().width;
double yScallingFactor = (float)screenSize.height / (float)img.size().height;
double minFactor = std::min(xScallingFactor, yScallingFactor);
cv::Mat temp;
cv::resize(img, temp, cv::Size(), minFactor, minFactor);
cv::moveWindow(windowTitle, screenZeroPoint.x, screenZeroPoint.y);
cv::imshow(windowTitle, temp);
}
int _tmain(int argc, _TCHAR* argv[])
{
cv::Mat img1 = cv::imread("D:\\temp\\test.png");
cv::Mat img2;
cv::bitwise_not(img1, img2);
cv::namedWindow("img1", CV_WINDOW_AUTOSIZE);
cv::setWindowProperty("img1", CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);
cv::namedWindow("img2");
while(cv::waitKey(1) != 'q')
{
cv::imshow("img1", img1);
cv::setWindowProperty("img1", CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN);
showWindowAlmostFullscreen(img2, "img2", cv::Size(1366, 768), cv::Point(260, 1080));
}
}
and the result:
Screen size and screen zero point (i don't know whether this is a correct name of this point - generally it's just a point in which there is screen (0,0) point) you can get using some other library or from windows control panel. Screen zero point will display when you will start moving screen:
If you use QT for writing your code, you can possibly utilize QT5's "Widget".
Here is a tutorial that will show you how to display an OpenCV image in a QT Widget.
Once you have that working you can then use something like this:
QScreen *screen = QGuiApplication::screens()[1]; // specify which screen to use
SecondDisplay secondDisplay = new SecondDisplay(); // your widget
** Add your code to display opencv image in widget here **
secondDisplay->move(screen->geometry().x(), screen->geometry().y());
secondDisplay->resize(screen->geometry().width(), screen->geometry().height());
secondDisplay->showFullScreen();
(Code found here on another SO answer)
I have not tried this myself, so I can't guarantee it will work, however, but it seems likely (if not a little overkill)
Hope this helps.
I wrote a simple OpenCV program that recovers my webcam video stream and display it on a simple window. I wante to resize this window to the resolution 256x256 but it changed it to 320x240.
Here's my source code :
#include <iostream>
#include <opencv/cv.h>
#include <opencv/highgui.h>
using namespace std;
int main(int argc, char** argv)
{
char key;
cvNamedWindow("Camera_Output", cv::WINDOW_NORMAL);
CvCapture *capture = cvCaptureFromCAM(CV_CAP_ANY);
cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_WIDTH, 256);
cvSetCaptureProperty(capture, CV_CAP_PROP_FRAME_HEIGHT, 256);
while(1){
IplImage *frame = cvQueryFrame(capture);
cvShowImage("Camera_Output", frame);
key = cvWaitKey(10);
if (key == 27){
break;
}
}
cvReleaseCapture(&capture);
cvDestroyWindow("Camera_Output");
return 0;
}
The output resolution is 320x240 and I want a 256x256 resolution. I think it's not possible because the camera manages its output video stream buffer and it has to keep the same ratio (width/height). What do you think about this idea ?
Is there a function which can force the resolution as a square resolution using OpenCV ?
Thanks a lot in advance for your help.
Seems like you video source does not handle 256x256 resolution. If you want to display it as such, you will have to crop the image yourself before displaying it.
Simple, you can do this by:
VideoCapture cap;
cap.open(0); // open your web-camera
cap.set(CV_CAP_PROP_FRAME_WIDTH, 256);
cap.set(CV_CAP_PROP_FRAME_HEIGHT, 256);
If this doesn't work, you need to resize it manually by calling cv::resize().
This will probably be a dumb question, but i really can't figure it out.
First of all: sorry for the vague title, i'm not really sure about how to describe my problem in a couple of words.
I'm using OpenCV 2.4.3 in MS Visual Studio, C++. I'm using the VideoCapture interface for capturing frames from my laptop webcam.
What my program should do is:
Loop on different poses of the user, for each pose:
wait that the user is in position (a getchar() waits for an input that says "i'm in position" by simply hitting enter)
read the current frame
extract a region of intrest from that frame
save the image in the ROI and then label it
Here is the code:
int main() {
Mat img, face_img, img_start;
Rect *face;
VideoCapture cam(0);
ofstream fout("dataset/dataset.txt");
if(!fout) {
cout<<"Cannot open dataset file! Aborting"<<endl;
return 1;
}
int count = 0; // Number of the (last + 1) image in the dataset
// Orientations are: 0°, +/- 30°, +/- 60°, +/-90°
// Distances are just two, for now
// So it is 7x2 images
cam.read(img_start);
IplImage image = img_start;
face = face_detector(image);
if(!face) {
cout<<"No face detected..? Aborting."<<endl;
return 2;
}
// Double ROI dimensions
face->x = face->x-face->width / 2;
face->y = face->y-face->height / 2;
face->width *= 2;
face->height *=2;
for(unsigned i=0;i<14;++i) {
// Wait for the user to get in position
getchar();
// Get the face ROI
cam.read(img);
face_img = Mat(img, *face);
// Save it
stringstream sstm;
string fname;
sstm << "dataset/image" << (count+i) << ".jpeg";
fname = sstm.str();
imwrite(fname,face_img);
//do some other things..
What i expect from it:
i stand in front of the camera when the program starts and it gets the ROI rectangle using the face_detector() function
when i'm ready, say in pose0, i hit enter and a picture is taken
from that picture a subimage is extracted and it is saved as image0.jpeg
loop this 7 times
What it does:
i stand in front of the camera when the program starts, nothing special here
i hit enter
the ROI is extracted not from the picture taken in that moment, but from the first one
At first, i used img in every cam.capture(), then i changed the first one in cam.capture(img_start) but that didn't help.
The second iteration of my code saves the image that should have been saved in the 1st, the 3rd iteration the one that should have been saved in the 2nd and so on.
I'm probably missing someting important from the VideoCapture, but i really can't figure it out, so here i am.
Thanks for any help, i really appreciate it.
The problem with your implementation is that the camera is not running freely and capturing images in real time. When you start up the camera, the videocapture buffer is filled up while waiting for you to read in the frames. Once the buffer is full, it doesn't drop old frames for new ones until you read and free up space in it.
The solution would be to have a separate capture thread, in addition to your "process" thread. The capture thread keeps reading in frames from the buffer whenever a new frame comes in and stores it in a "recent frame" image object. When the process thread needs the most recent frame (i.e. when you hit Enter), it locks a mutex for thread safety, copies the most recent frame into another object and frees the mutex so that the capture thread continues reading in new frames.
#include <iostream>
#include <stdio.h>
#include <thread>
#include <mutex>
#include <opencv2/objdetect/objdetect.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>
using namespace std;
using namespace cv;
void camCapture(VideoCapture cap, Mat* frame, bool* Capture){
while (*Capture==true) {
cap >> *frame;
}
cout << "camCapture finished\n";
return;
}
int main() {
VideoCapture cap(0); // open the default camera
if (!cap.isOpened()) // check if we succeeded
return -1;
Mat *frame, SFI, Input;
frame = new Mat;
bool *Capture = new bool;
*Capture = true;
//your capture thread has started
thread captureThread(camCapture, cap, frame, Capture);
mtx.lock();
imshow(*frame,current_frame);
mtx.unlock();
//Terminate the thread
mtx.lock();
*Capture = false;
mtx.unlock();
captureThread.join();
return 0;
}
This is the code that I wrote from the above advice. I hope someone can get help from this.
When you are capturing the image continuously, no captured frame will be stored in the opencv buffer, such that there will be no lag in streaming.
If you take screenshot/capture image with some time gap inbetween, the captured image will be first stored in the opencv buffer, after that the image is retrieved from the buffer.
When the buffer is full, when you are calling captureObject >> matObject, the last frame from the image is returned, not the current frame in the capturecard/webcam.
So only you are seeing a lag in your code. This issue can be resolved by taking screenshot based on the frames per second (fps) value of the webcam and time taken to capture the screenshot.
The time taken to read frame from buffer is very less, Measure the time taken to take the screenshot. If it is lesser than the fps we can assume that is read from buffer else it means it is captured from webcam.
Sample Code:
For capturing a recent screenshot from webcam.
#include <opencv2/opencv.hpp>
#include <time.h>
#include <thread>
#include <chrono>
using namespace std;
using namespace cv;
int main()
{
struct timespec start, end;
VideoCapture cap(-1); // first available webcam
Mat screenshot;
double diff = 1000;
double fps = ((double)cap.get(CV_CAP_PROP_FPS))/1000;
while (true)
{
clock_gettime(CLOCK_MONOTONIC, &start);
//camera.grab();
cap.grab();// can also use cin >> screenshot;
clock_gettime(CLOCK_MONOTONIC, &end);
diff = (end.tv_sec - start.tv_sec)*1e9;
diff = (diff + (end.tv_nsec - start.tv_nsec))*1e-9;
std::cout << "\n diff time " << diff << '\n';
if(diff > fps)
{
break;
}
}
cap >> screenshot; // gets recent frame, can also use cap.retrieve(screenshot);
// process(screenshot)
cap.release();
screenshot.release();
return 0;
}