Using webcam video as texture in OpenGL + some modification to run it with current opencv on Linux.

main.cpp

// Original gist was here: https://gist.github.com/Ashwinning/baeb0835624fedc2e5b809d42417b70e
// Modified from "Video Texture" code
// Copyright (C) 2009  Arsalan Malik (arsalank2@hotmail.com)
//
// On Mac OS X, compile with:
// g++ -o VideoTexture VideoTexture.cpp -framework OpenGL -framework Glut -I
// /usr/local/include/opencv/ $(pkg-config --libs opencv)
//////////////////////////////////////////////////////////////////////////////
// On Linux,
// g++ -o example-opengl example-opengl.cpp -I/usr/include/opencv4
// `pkg-config opencv4 --libs` -lGL -lGLU -lglut  -lglfw  -lGL -lX11 -lpthread -lXrandr -lXi -ldl
//////////////////////////////////////////////////////////////////////////////

// Open CV includes
//#include <cv.h>

#include "opencv2/core/utility.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"

#include <opencv2/videoio/videoio_c.h>

//#include <highgui.h>

// Standard includes
#include <stdio.h>
#include <string.h>
#include <assert.h>

// OpenGL/Glut includes
#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

// Timing includes
#include <sys/time.h>

#define KEY_ESCAPE 27

//CvCapture *g_Capture;
cv::VideoCapture g_Capture;

GLint g_hWindow;

// Frame size
int frame_width = 640;
int frame_height = 480;

// current frames per second, slightly smoothed over time
double fps;
// show mirror image
bool mirror = true;

// Return current time in seconds
double current_time_in_seconds();
// Initialize glut window
GLvoid init_glut();
// Glut display callback, draws a single rectangle using video buffer as
// texture
GLvoid display();
// Glut reshape callback
GLvoid reshape(GLint w, GLint h);
// Glut keyboard callback
GLvoid key_press(unsigned char key, GLint x, GLint y);
// Glut idle callback, fetches next video frame
GLvoid idle();

double current_time_in_seconds()
{
    timeval timer;
    gettimeofday(&timer, NULL);
    double seconds = 1e-6 * timer.tv_usec + timer.tv_sec;
    return seconds;
}

GLvoid init_glut()
{

    glClearColor(0.0, 0.0, 0.0, 0.0);

    // Set up callbacks
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutKeyboardFunc(key_press);
    glutIdleFunc(idle);
}

GLvoid display(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glEnable(GL_TEXTURE_2D);
    // These are necessary if using glTexImage2D instead of gluBuild2DMipmaps
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);

    // Set Projection Matrix
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0, frame_width, frame_height, 0);

    // Switch to Model View Matrix
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    // Draw a textured quad
    glBegin(GL_QUADS);
    glTexCoord2f(0.0f, 0.0f);
    glVertex2f(0.0f, 0.0f);
    glTexCoord2f(1.0f, 0.0f);
    glVertex2f(frame_width, 0.0f);
    glTexCoord2f(1.0f, 1.0f);
    glVertex2f(frame_width, frame_height);
    glTexCoord2f(0.0f, 1.0f);
    glVertex2f(0.0f, frame_height);
    glEnd();

    glFlush();
    glutSwapBuffers();
}

GLvoid reshape(GLint w, GLint h)
{
    glViewport(0, 0, w, h);
}

GLvoid key_press(unsigned char key, int x, int y)
{
    switch (key)
    {
    case 'f':
        printf("fps: %g\n", fps);
        break;
    case 'm':
        mirror = !mirror;
        break;
    case KEY_ESCAPE:
        //cvReleaseCapture(&g_Capture);
        glutDestroyWindow(g_hWindow);
        exit(0);
        break;
    }
    glutPostRedisplay();
}

GLvoid idle()
{
    // start timer
    double start_seconds = current_time_in_seconds();

    // Capture next frame, this will almost always be the limiting factor in the
    // framerate, my webcam only gets ~15 fps
    //IplImage *image; // = cvQueryFrame(g_Capture);
    cv::Mat image;

    //frame = cvQueryFrame( capture ); //assegna frame
    g_Capture.read(image);

    // Of course there are faster ways to do this with just opengl but this is to
    // demonstrate filtering the video before making the texture
    if (mirror)
    {
        // cvFlip(image, NULL, 1);
        flip(image, image, +1);
    }

    // Image is memory aligned which means we there may be extra space at the end
    // of each row. gluBuild2DMipmaps needs contiguous data, so we buffer it here
    char *buffer = new char[image.cols * image.rows * image.channels()];
    int step = image.step; //widthStep;
    int height = image.rows;
    int width = image.cols;
    int channels = image.channels();
    char *data = (char *)image.data; //imageData;
    // memcpy version below seems slightly faster
    //for(int i=0;i<height;i++)
    //for(int j=0;j<width;j++)
    //for(int k=0;k<channels;k++)
    //{
    //  buffer[i*width*channels+j*channels+k] = data[i*step+j*channels+k];
    //}
    for (int i = 0; i < height; i++)
    {
        memcpy(&buffer[i * width * channels], &(data[i * step]), width * channels);
    }

    // Create Texture
    glTexImage2D(
        GL_TEXTURE_2D,
        0,
        GL_RGB,
        image.cols,
        image.rows,
        0,
        GL_BGR,
        GL_UNSIGNED_BYTE,
        buffer);

    // Clean up buffer
    delete[] buffer;

    // Update display
    glutPostRedisplay();

    double stop_seconds = current_time_in_seconds();
    fps = 0.9 * fps + 0.1 * 1.0 / (stop_seconds - start_seconds);
}

int main(int argc, char *argv[])
{

    // Create OpenCV camera capture
    // If multiple cameras are installed, this takes "first" one
    //g_Capture = cvCaptureFromCAM(0);
    //assert(g_Capture);

    g_Capture.open(0); // open the default camera
    if (!g_Capture.isOpened())
    {
        //std::cout << "Capture not open successfully 0" << std::endl;
        printf("Capture not open successfully");
        getchar();
        //return -1;
    }

    // capture properties
    //frame_height = (int)cvGetCaptureProperty(g_Capture, CV_CAP_PROP_FRAME_HEIGHT);
    //frame_width = (int)cvGetCaptureProperty(g_Capture, CV_CAP_PROP_FRAME_WIDTH);

    //setting the dimensions of webcam frame
    frame_width = g_Capture.get(cv::CAP_PROP_FRAME_WIDTH);
    frame_height = g_Capture.get(cv::CAP_PROP_FRAME_HEIGHT);

    // Create GLUT Window
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(frame_width, frame_height);

    g_hWindow = glutCreateWindow("Video Texture");

    // Initialize OpenGL
    init_glut();

    glutMainLoop();

    return 0;
}

Thanks for code