Question

This may seem trivial for most people but I am getting problems in determining the exact size i.e. the exact width and height of my video frames. I used cvGetSize but I am probably coding it inaccurately because I am getting an error. Is it possible to output the values of the width and height of my frames as I have included in my code below? Please I would appreciate it if someone could advise me on this.

#include "cv.h"
#include "highgui.h"
#include "iostream"

using namespace std;
int main( int argc, char* argv ) {

CvCapture *capture = NULL;
capture = cvCaptureFromAVI("C:\\walking\\lady walking.avi");
if(!capture){
    return -1;
}

IplImage* color_frame = NULL;
IplImage* gray_frame = NULL ;

int thresh_frame = 17;

int frameCount=0;//Counts every 5 frames
cvNamedWindow( "contours", CV_WINDOW_AUTOSIZE );

while(1) {
    color_frame = cvQueryFrame( capture );//Grabs the frame from a file
    if( !color_frame ) break;
    gray_frame = cvCreateImage(cvSize(color_frame->width, color_frame->height), color_frame->depth, 1);
    if( !color_frame ) break;// If the frame does not exist, quit the loop

    frameCount++;
    if(frameCount==5)
    {
        cvCvtColor(color_frame, gray_frame, CV_BGR2GRAY);
        cvThreshold(gray_frame, gray_frame, thresh_frame, 255, CV_THRESH_TOZERO_INV);

        cvGetSize(gray_frame);
        int w;
        int h;

        cvSize(w,h);

        cout <<" dimensions " <<  cvSize(w, h) << endl;

        cvShowImage("contours", gray_frame);
        frameCount=0;
    }
    char c = cvWaitKey(33);
    if( c == 27 ) break;
}

cvReleaseImage(&color_frame);
cvReleaseImage(&gray_frame);
cvReleaseCapture( &capture );
cvDestroyWindow( "contours" );

return 0;
}

Answer 1

Try the following code 🙂
The key point is the usage of cvGetSize function and CvSize structure.

#include "cv.h"
#include "highgui.h"
#include "iostream"

using namespace std;
int main( int argc, char* argv ) {

CvCapture *capture = NULL;
capture = cvCaptureFromAVI("C:\\walking\\lady walking.avi");
if(!capture){
    return -1;
}

IplImage* color_frame = NULL;
IplImage* gray_frame = NULL ;

int thresh_frame = 17;

int frameCount=0;//Counts every 5 frames
cvNamedWindow( "contours", CV_WINDOW_AUTOSIZE );

while(1) {
    color_frame = cvQueryFrame( capture );//Grabs the frame from a file
    if( !color_frame ) break;
    gray_frame = cvCreateImage(cvSize(color_frame->width, color_frame->height), color_frame->depth, 1);
    if( !color_frame ) break;// If the frame does not exist, quit the loop

    frameCount++;
    if(frameCount==5)
    {
        cvCvtColor(color_frame, gray_frame, CV_BGR2GRAY);
        cvThreshold(gray_frame, gray_frame, thresh_frame, 255, CV_THRESH_TOZERO_INV);

        CvSize dim = cvGetSize(gray_frame);

        cout <<" dimensions:: height:" <<  dim.height<<" width:"<< dim.width<< endl;

        cvShowImage("contours", gray_frame);
        frameCount=0;
    }
    char c = cvWaitKey(33);
    if( c == 27 ) break;
}

cvReleaseImage(&color_frame);
cvReleaseImage(&gray_frame);
cvReleaseCapture( &capture );
cvDestroyWindow( "contours" );

return 0;
}