This is the 3rd question for today as I am still struggling. The problem is: Visual Studio is giving the error on line 2. It says:
Error: name must be a namespace name
This is my code, this should open the webcam and it should take frames.
What is wrong here?
#include "opencv.hpp"
using namespace cv;
int main(int argc, char** argv)
{
VideoCapture cap;
// open the default camera, use something different from 0 otherwise;
// Check VideoCapture documentation.
if (!cap.open(0))
return 0;
for (;;)
{
Mat frame;
cap >> frame;
if (frame.empty()) break; // end of video stream
imshow("this is you, smile! :)", frame);
if (waitKey(1) == 27) break; // stop capturing by pressing ESC
}
// the camera will be closed automatically upon exit
// cap.close();
return 0;
}
Related
I have some code I think should be working using open CV to detect a set of fiducials. For some reason, I cant get my code to run. It gives the error "Unable to stop the stream: Invalid argument"
#include "opencv2/opencv.hpp"
using namespace cv;
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/aruco.hpp>
int main(int argc, char** argv)
{
Mat markerImage;
VideoCapture cap;
// open the default camera, use something different from 0 otherwise;
// Check VideoCapture documentation.
if(!cap.open(1))
return 0;
for(;;)
{
Mat frame;
cap >> frame;
if( frame.empty() ) break; // end of video stream
std::vector<int> markerIds;
std::vector<std::vector<cv::Point2f>> markerCorners, rejectedCandidates;
cv::Ptr<cv::aruco::DetectorParameters> parameters = cv::aruco::DetectorParameters::create();
cv::Ptr<cv::aruco::Dictionary> dictionary = cv::aruco::getPredefinedDictionary(cv::aruco::DICT_5X5_50);
cv::aruco::detectMarkers(frame, dictionary, markerCorners, markerIds, parameters, rejectedCandidates);
cv::aruco::drawDetectedMarkers(frame, markerCorners, markerIds);
imshow("Camera)", frame);
if( waitKey(10) == 27 ) break; // stop capturing by pressing ESC
}
// the camera will be closed automatically upon exit
// cap.close();
return 0;
}
I tried to get it running, but it didn't do anything, didn't show up errors and automatically terminated the program.
#include"opencv2/core/core.hpp"
#include"opencv2/highgui/highgui.hpp"
#include"opencv2/imgproc/imgproc.hpp"
#include<stdio.h>
int main(int argc, char* argv)
{
cvNamedWindow("Example2", CV_WINDOW_AUTOSIZE);
CvCapture* capture = cvCreateFileCapture("C:/Users/Nam/Pictures/YALQ6371.MP4");
IplImage* frame;
while (1){
frame = cvQueryFrame(capture);
if (!frame) break;
cvShowImage("Example2", frame);
char c = cvWaitKey(33);
if (c == 27) break;
}
cvReleaseCapture(&capture);
cvDestroyWindow("Example2");
return 0;
}
Try using imshow instead of cvShowImage, but don't forget to add using namespace cv; at the beginning.
Linux Debian 10 + OpenCV 320.
Very basic sample to play a video but the application soon ends without open a new window and witout errors.
My tests with same videos but in different types: mp4 and webm. The video are correctly shown by VLC and other video players.
#include <stdio.h>
#include <opencv2/opencv.hpp>
#include <opencv2/highgui.hpp>
using namespace cv;
int main(int argc, char** argv )
{
// check
if ( argc != 2 )
{
printf("usage: %s <Video_Path>\n", argv[0]);
return -1;
}
printf("Video: %s\n", argv[1]);
// load video
VideoCapture cap ( argv[1]);
if (!cap.isOpened()){
printf("Error opening video\n");
}
Mat frame;
while(1){
// cap.read(frame);
cap >> frame;
if (frame.empty()){
printf(".. frame err\n");
return -1;
}
imshow("Live", frame);
if (waitKey(5)>=0) break;
}
printf("end\n");
return 0;
}
The output is:
$ ./DisplayVideo 20200313_152914.webm
Video: 20200313_152914.webm
end
I solved casting to char:
if ((char)(waitKey(1))>=0){
I receive an error "SIGABRT ERROR" when the code is trying to save the image on the HD.
I'm working with a MacBook Pro Mountain Lion on last XCODE and the libraries are well reconfigured.
Someone has a solution or some ideas?
#include "cv.h"
#include "highgui.h"
#include <stdio.h>
using namespace cv;
// A Simple Camera Capture Framework
int main() {
CvCapture* capture = cvCaptureFromCAM( CV_CAP_ANY );
if ( !capture ) {
fprintf( stderr, "ERROR: capture is NULL \n" );
getchar();
return -1;
}
// Create a window in which the captured images will be presented
cvNamedWindow( "mywindow", CV_WINDOW_AUTOSIZE );
// Show the image captured from the camera in the window and repeat
while ( 1 ) {
// Get one frame
IplImage* frame = cvQueryFrame( capture );
if ( !frame ) {
fprintf( stderr, "ERROR: frame is null...\n" );
getchar();
break;
}
cvShowImage( "mywindow", frame );
// Do not release the frame!
if ( (cvWaitKey(10) & 255) == 's' ) {
CvSize size = cvGetSize(frame);
IplImage* img= cvCreateImage(size, IPL_DEPTH_16S, 1);
img = frame;
cvSaveImage("matteo.jpg",&img);
}
if ( (cvWaitKey(10) & 255) == 27 ) break;
}
// Release the capture device housekeeping
cvReleaseCapture( &capture );
cvDestroyWindow( "mywindow" );
return 0;
}
The problem is that you are mixing your pointer syntax. You are creating a new IplImage with IplImage* img= cvCreateImage(size, IPL_DEPTH_16S, 1); but on the following line, you lose this structure as you overwrite the pointer img with frame.
The code causing your sigabrt is where you're sending a pointer to a pointer in
cvSaveImage("matteo.jpg",&img);. You should not do &img as img already is a pointer. The following is correct:
cvSaveImage("matteo.jpg",img);
There is actually no reason for you to create a new IplImage unless you want to do some preprocessing before saving it to file.
I modified your if-clause to the following which works fine on my computer:
if ( cvWaitKey(10) < 0 ) {
cvSaveImage("matteo.jpg",frame);
}
I have spent several days searching the internet for the right solution with simple keyboard input. There was always some lag / delay while using cv::waitKey.
The solution I have found is with adding Sleep(5) just after capturing the frame from webcam.
The below example is a combination of different forum threads.
It works without any lag / delay. Windows OS.
Press "q" to capture and save the frame.
There is a webcam feed always present. You can change the sequence to show the captured frame / image.
PS "tipka" - means "key" on the keyboard.
Regards, Andrej
#include <opencv2/opencv.hpp>
#include <iostream>
#include <stdio.h>
#include <windows.h> // For Sleep
using namespace cv;
using namespace std;
int ct = 0;
char tipka;
char filename[100]; // For filename
int c = 1; // For filename
int main(int, char**)
{
Mat frame;
//--- INITIALIZE VIDEOCAPTURE
VideoCapture cap;
// open the default camera using default API
cap.open(0);
// OR advance usage: select any API backend
int deviceID = 0; // 0 = open default camera
int apiID = cv::CAP_ANY; // 0 = autodetect default API
// open selected camera using selected API
cap.open(deviceID + apiID);
// check if we succeeded
if (!cap.isOpened()) {
cerr << "ERROR! Unable to open camera\n";
return -1;
}
//--- GRAB AND WRITE LOOP
cout << "Start grabbing" << endl
<< "Press a to terminate" << endl;
for (;;)
{
// wait for a new frame from camera and store it into 'frame'
cap.read(frame);
if (frame.empty()) {
cerr << "ERROR! blank frame grabbed\n";
break;
}
Sleep(5); // Sleep is mandatory - for no leg!
// show live and wait for a key with timeout long enough to show images
imshow("CAMERA 1", frame); // Window name
tipka = cv::waitKey(30);
if (tipka == 'q') {
sprintf_s(filename, "C:/Images/Frame_%d.jpg", c); // select your folder - filename is "Frame_n"
cv::waitKey(10);
imshow("CAMERA 1", frame);
imwrite(filename, frame);
cout << "Frame_" << c << endl;
c++;
}
if (tipka == 'a') {
cout << "Terminating..." << endl;
Sleep(2000);
break;
}
}
// the camera will be deinitialized automatically in VideoCapture destructor
return 0;
}
I have been trying to get a real basic video player working using the Open CV API. Everything seems to run smoothly until the end of a video clip, then i get this error:
OpenCV Error: Bad flag in unknown function, file ........\ocv\opencv\modules\core\src\array.cpp
This creates a break in the code at imshow("video", frame), i find this wierd as this is the part that effectively plays the video so why does it only kick up a fuss at the end of the clip?? I found that it seems to give me this error in the last 90% of every video i play so at the moment im working around it by telling it to stop once 90% of the clip has played but this isnt very good programming so can anyone send some suggestions/help?
I have looked at other peoples post on this matter and none of the solution suggested have worked for me as of yet.
Heres my code...its only an experimentation piece so im sorry if its a bit messy:
Thanks for any help in advance
#include <cv.h>
#include <cxcore.h>
#include <highgui.h>
#include <direct.h>
#include <iostream>
using namespace cv;
void onTrackBarSlide(int);
double the_next_play_frame;
VideoCapture video("test.MOV"); // open the video file
int main(int, char**)
{
if(!video.isOpened()) // check if we succeeded
{
return -1;
}
int no_of_frames = video.get(CV_CAP_PROP_FRAME_COUNT); //total number of frames in video
std::cout << no_of_frames << std::endl;
std::cout << video.get(CV_CAP_PROP_FPS) << std::endl;
namedWindow("Video", 1);
cvCreateTrackbar("trackbar", "Video", 0, 40, onTrackBarSlide);
double stop_at = no_of_frames * 0.999;
for(;;){
if(the_next_play_frame >= double(stop_at))
{
break;
}
Mat frame;
video >> frame; // get a new frame from camera
imshow("Video", frame); // <---------- place where break/error occurs
if(waitKey(30) >= 0)
{
break;
}
}
return 0;
}
void onTrackBarSlide(int pos)
{
std::cout << getTrackbarPos("trackbar", "Video") << std::endl;
double frameratio = video.get(CV_CAP_PROP_FRAME_COUNT)/40; //10005 is the maximum value the slider can actual hold
double next_play_frame = frameratio * getTrackbarPos("trackbar", "Video");
video.set(CV_CAP_PROP_POS_FRAMES,next_play_frame);
the_next_play_frame = next_play_frame;
}
VideoCapture video("test.MOV"); // open the video file
int main(int, char**)
{
if(!video.isOpened()) // check if we succeeded
{
return -1;
}
}
Try put the VideoCapture instantiation inside main.
int main(){
VideoCapture video("test.MOV"); // open the video file
...
}