OpenCV VideoCapture Video Capture cannot start, trying to use laptop camera - c++

Question

Hey everyone so I was given this code by my professor to look over for using videocapture with OpenCV but it's not wokring for me. The proffessor was able to run it in class and he used his laptop camera, but the same code is not working for me. Is there anything wrong with this code? Or do I have to do some sort of initial setup with my laptop camera using openCV? Any help would be appreciated.
#include <opencv2/opencv.hpp> //for OpenCV 3.x
#include <opencv/highgui.h> //for OpenCV 3.x
#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/gl.h>
#include <GL/glut.h>
#endif
#include <cstdio>
cv::VideoCapture *cap = NULL;
int width = 640;
int height = 480;
cv::Mat image;
/*------------ function displaying x,y,z coordinate system ----------*/
void drawAxes(float length)
{
glPushAttrib(GL_POLYGON_BIT | GL_ENABLE_BIT | GL_COLOR_BUFFER_BIT) ;
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE) ;
glDisable(GL_LIGHTING) ;
glBegin(GL_LINES) ;
glColor3f(1,0,0) ; //x: red
glVertex3f(0,0,0) ;
glVertex3f(length,0,0);
glColor3f(0,1,0) ; //y: blue
glVertex3f(0,0,0) ;
glVertex3f(0,length,0);
glColor3f(0,0,1) ; //z: green
glVertex3f(0,0,0) ;
glVertex3f(0,0,length);
glEnd() ;
glPopAttrib() ;
}
/*---------------- display --------------*/
void display()
{
glClear( GL_COLOR_BUFFER_BIT ); // clear window
// cv::Mat stores data, has to flip it before displaying it
cv::Mat tempimage;
/*
flip(image, image, 0); // vertically
flip(image, image, +1); // horizontally
// or 90 degree clock wise
transpose(image, image);
flip(image, image, +1);
// or 90 degree counter clock wise
transpose(image, image);
flip(image, image, 0);
*/
cv::flip(image, tempimage, 0);
glDrawPixels(tempimage.size().width,tempimage.size().height,GL_BGR,GL_UNSIGNED _BYTE,tempimage.ptr());
//set viewport
glViewport(0, 0, tempimage.size().width, tempimage.size().height);
//set projection matrix using intrinsic camera params
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
/*
void gluPerspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar);
*/
gluPerspective(60, tempimage.size().width*1.0/tempimage.size().height, 1, 20);
//you will have to set modelview matrix using extrinsic camera params
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
/*gluLookAt (cameraX, cameraY, cameraZ, lookAtX, lookAtY, lookAtZ, upX, upY, upZ);
https://www.khronos.org/registry/OpenGL-Refpages/gl2.1/xhtml/ gluLookAt.xml
*/
gluLookAt(3, 3, 3, 0, 0, 0, 0, 1, 0); //(upX, upY, upZ) = (0, 1, 0) always
//now that the camera params have been set, draw your 3D shapes
//first, save the current matrix
glPushMatrix();
//move to the position where you want the 3D object to go
glTranslatef(0, 0, 0); //this is an arbitrary position for demonstration
//you will need to adjust your transformations to match the positions where
//you want to draw your objects(i.e. chessboard center, chessboard corners)
glutSolidTeapot(0.2);
glutSolidSphere(.3, 100, 100);
drawAxes(1.0);
glPopMatrix();
// show the rendering on the screen
glutSwapBuffers();
// post the next redisplay
glutPostRedisplay();
}
void reshape( int w, int h )
{
// set OpenGL viewport (drawable area)
glViewport( 0, 0, w, h );
}
void mouse( int button, int state, int x, int y )
{
if ( button == GLUT_LEFT_BUTTON && state == GLUT_UP )
{
}
}
void keyboard( unsigned char key, int x, int y )
{
switch ( key )
{
case 'q':
// quit when q is pressed
exit(0);
break;
default:
break;
}
}
void idle()
{
// grab a frame from the camera
(*cap) >> image;
}
int main( int argc, char **argv )
{
int w,h;
if ( argc == 1 ) {
// start video capture from camera
cap = new cv::VideoCapture(0);
} else if ( argc == 2 ) {
// start video capture from file
cap = new cv::VideoCapture(argv[1]);
} else {
fprintf( stderr, "usage: %s [<filename>]\n", argv[0] );
return 1;
}
// check that video is opened
if ( cap == NULL || !cap->isOpened() ) {
fprintf( stderr, "could not start video capture\n" );
return 1;
}
// get width and height
w = (int) cap->get( CV_CAP_PROP_FRAME_WIDTH );
h = (int) cap->get( CV_CAP_PROP_FRAME_HEIGHT );
// On Linux, there is currently a bug in OpenCV that returns
// zero for both width and height here (at least for video from file)
// hence the following override to global variable defaults:
width = w ? w : width;
height = h ? h : height;
// initialize GLUT
glutInit( &argc, argv );
glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE );
glutInitWindowPosition( 20, 20 );
glutInitWindowSize( width, height );
glutCreateWindow( "OpenGL / OpenCV Example" );
// set up GUI callback functions
glutDisplayFunc( display );
glutReshapeFunc( reshape );
glutMouseFunc( mouse );
glutKeyboardFunc( keyboard );
glutIdleFunc( idle );
// start GUI loop
glutMainLoop();
return 0;
}
EDIT:
I think i know the problem. It's because Im running a VM and the VM doesnt detect the camera. But how would I run this code with a video file? I also tried that but it didnt work.