How to get resolution of camera - c++

Question

How to get the resolution of camera? Can somebody give me some suggestion.
Only i can do is the following,but it takes too much time to get the resolution.
The code's sequence look like this:
a.Open the camerra
b.Change the camera's resolution, and check the reuslt
void GetResolution( const int& countOfCamera, resolution_t (&resoulationTemp)[MAX_RESOLUTION] ){
VideoCapture *pVideoCaptures[MAX_CAMERA] = {NULL};
bool ret1 = false;
bool ret2 = false;
for ( int j=0; j<countOfCamera; ++j ) {
pVideoCaptures[j] = new VideoCapture(j);
/*==========================================================================
*If we don't do this, we will not open the Camera correctly
===========================================================================*/
pVideoCaptures[j]->set( CV_CAP_PROP_FRAME_WIDTH, defaultResolution.width );
pVideoCaptures[j]->set ( CV_CAP_PROP_FRAME_HEIGHT, defaultResolution.height );
}
for ( int i=0; i<MAX_RESOLUTION; ++i ) {
for ( int j=0; j<countOfCamera; ++j ) {
ret1 = pVideoCaptures[j]->set( CV_CAP_PROP_FRAME_WIDTH, resolutions[i].width );
ret2 = pVideoCaptures[j]->set ( CV_CAP_PROP_FRAME_HEIGHT, resolutions[i].height );
if ( !(ret1 && ret2) ) { //The resolution is not OK
break; //Check the next resolution
} else if ( j == ( countOfCamera -1 ) ) { //The resolution is OK for all camera,then store it.
resoulationTemp[i].width = resolutions[i].width;
resoulationTemp[i].height = resolutions[i].height;
} else {
//Do nothing
}
}
}
for ( int j=0; j<countOfCamera; ++j ) //Release the memory
{
pVideoCaptures[j]->release();
delete pVideoCaptures[j];
pVideoCaptures[j] = NULL;
}
}

Answer 1

Unfortunately there is no convenient way to get supported resolutions list for the particular camera by the opencv API (as it supports so many platforms and so many video capturing backends). Even your code will suffer from this, read the sources of videoio.hpp. But most of the digital video devices supports standard resolutions, you can simply select from them. Another way to get actual list of supported formats is to use 3rd party libraries, for the instance Qt solves this task by the couple of calls.