example of mixing opencv and opengl programs

cv_gl_1.c

#include <opencv2/opencv.hpp>
#include <GL/glut.h>

cv::VideoCapture cap;
void opencv_init()
{
  cap = cv::VideoCapture(0);
}

void opencv_loop()
{
  cv::Mat frame;
  cap.read(frame);
  cv::imshow("Frame", frame);

  unsigned char key = cv::waitKey(1);
  if ( key == 27 )
  {
    exit(1);
  }
}

void keyboard(unsigned char key, int x, int y)
{
  if ( key == 27 )
  {
    printf("exitting");
    exit(1);
  }
}

void init(int width, int height)
{
  glClearColor(0.0, 0.0, 0.0, 1.0);
  glEnable(GL_DEPTH_TEST);

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(45.0, float(width)/float(height), 0.1, 100.0);
}

void display(void)
{

  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  gluLookAt(0.0, 1.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
  glColor3f(1.0, 0.0, 0.0);
  glutWireTeapot(1.0);
  glFlush();
}

void reshape(int width, int height)
{
  glViewport(0, 0, width, height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(45.0, float(width)/float(height), 0.1, 100.0);
}

void idle()
{
  printf("running within idle callback\n");
  opencv_loop();
}

int main (int argc, char **argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize(300,300);
  glutInitWindowPosition(100, 100);
  glutCreateWindow("teapot");
  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutKeyboardFunc(keyboard);
  init(300, 300);
  glutIdleFunc(idle);
  opencv_init();
  glutMainLoop();
  return 0;
}

cv_gl_1.py

#!/usr/bin/env python
#-*- coding: utf-8 -*-

import cv2
from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.GLU import *

cap = None
# Loading Camera and Nose image and Creating mask
def opencv_init():
    global cap
    cap = cv2.VideoCapture(0)

def opencv_loop():
    global cap
    _, frame = cap.read()
    cv2.imshow("Frame", frame)

    key = cv2.waitKey(1)
    if key == 27:
        # break
        sys.exit(1)

def idle():
    print("running within idle callback")
    opencv_loop()

def main():
    glutInit(sys.argv)
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE | GLUT_DEPTH)
    glutInitWindowSize(300, 300)     # window size
    glutInitWindowPosition(100, 100) # window position
    glutCreateWindow(b"teapot")      # show window
    glutDisplayFunc(display)         # draw callback function
    glutReshapeFunc(reshape)         # resize callback function
    glutKeyboardFunc(keyboard)       # Keyboard event callback
    init(300, 300)
    i = 0
    glutIdleFunc(idle)
    opencv_init()
    glutMainLoop();

def keyboard(key, x, y):
    if key == chr(27):
        print("exitting")
        sys.exit()

def init(width, height):
    """ initialize """
    glClearColor(0.0, 0.0, 0.0, 1.0)
    glEnable(GL_DEPTH_TEST) # enable shading

    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    ##set perspective
    gluPerspective(45.0, float(width)/float(height), 0.1, 100.0)

def display():
    """ display """
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glMatrixMode(GL_MODELVIEW)
    glLoadIdentity()
    ##set camera
    gluLookAt(0.0, 1.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0)
    ##draw a teapot
    glColor3f(1.0, 0.0, 0.0)
    glutWireTeapot(1.0)   # wireframe
    glFlush()  # enforce OpenGL command

def reshape(width, height):
    """callback function resize window"""
    glViewport(0, 0, width, height)
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    gluPerspective(45.0, float(width)/float(height), 0.1, 100.0)

if __name__ == "__main__":
    main()

cv_gl_2.c

#include <opencv2/opencv.hpp>
#include <GL/glut.h>
#include <GL/freeglut.h> // for glutMainLoopEvent

cv::VideoCapture cap;
void opencv_init()
{
  cap = cv::VideoCapture(0);
}

void opencv_loop()
{
  cv::Mat frame;
  cap.read(frame);
  cv::imshow("Frame", frame);

  unsigned char key = cv::waitKey(1);
  if ( key == 27 )
  {
    exit(1);
  }
}

void keyboard(unsigned char key, int x, int y)
{
  if ( key == 27 )
  {
    printf("exitting");
    exit(1);
  }
}

void init(int width, int height)
{
  glClearColor(0.0, 0.0, 0.0, 1.0);
  glEnable(GL_DEPTH_TEST);

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(45.0, float(width)/float(height), 0.1, 100.0);
}

void display(void)
{

  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  gluLookAt(0.0, 1.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
  glColor3f(1.0, 0.0, 0.0);
  glutWireTeapot(1.0);
  glFlush();
}

void reshape(int width, int height)
{
  glViewport(0, 0, width, height);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(45.0, float(width)/float(height), 0.1, 100.0);
}

int main (int argc, char **argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize(300,300);
  glutInitWindowPosition(100, 100);
  glutCreateWindow("teapot");
  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutKeyboardFunc(keyboard);
  init(300, 300);
  int i = 0;
  opencv_init();
  while (true)
  {
    printf("running within while loop %d\n", i);
    glutMainLoopEvent();
    opencv_loop();
    i++;
  }
  return 0;
}

cv_gl_2.py

#!/usr/bin/env python
#-*- coding: utf-8 -*-

import cv2
from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.GLU import *

cap = None
# Loading Camera and Nose image and Creating mask
def opencv_init():
    global cap
    cap = cv2.VideoCapture(0)

def opencv_loop():
    global cap
    _, frame = cap.read()
    cv2.imshow("Frame", frame)

    key = cv2.waitKey(1)
    if key == 27:
        # break
        sys.exit(1)

def main():
    glutInit(sys.argv)
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE | GLUT_DEPTH)
    glutInitWindowSize(300, 300)     # window size
    glutInitWindowPosition(100, 100) # window position
    glutCreateWindow(b"teapot")      # show window
    glutDisplayFunc(display)         # draw callback function
    glutReshapeFunc(reshape)         # resize callback function
    glutKeyboardFunc(keyboard)       # Keyboard event callback
    init(300, 300)
    i = 0
    opencv_init()
    while True:
        print("running within while loop {}".format(i))
        glutMainLoopEvent()
        opencv_loop()
        i += 1

def keyboard(key, x, y):
    if key == chr(27):
        print("exitting")
        sys.exit()

def init(width, height):
    """ initialize """
    glClearColor(0.0, 0.0, 0.0, 1.0)
    glEnable(GL_DEPTH_TEST) # enable shading

    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    ##set perspective
    gluPerspective(45.0, float(width)/float(height), 0.1, 100.0)

def display():
    """ display """
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glMatrixMode(GL_MODELVIEW)
    glLoadIdentity()
    ##set camera
    gluLookAt(0.0, 1.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0)
    ##draw a teapot
    glColor3f(1.0, 0.0, 0.0)
    glutWireTeapot(1.0)   # wireframe
    glFlush()  # enforce OpenGL command

def reshape(width, height):
    """callback function resize window"""
    glViewport(0, 0, width, height)
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    gluPerspective(45.0, float(width)/float(height), 0.1, 100.0)

if __name__ == "__main__":
    main()

Makefile

all: cv_gl_1 cv_gl_2

cv_gl_1: cv_gl_1.c
	g++ -o cv_gl_1 cv_gl_1.c `pkg-config opencv --cflags --libs` -lGL -lGLU -lglut

cv_gl_2: cv_gl_2.c
	g++ -o cv_gl_2 cv_gl_2.c `pkg-config opencv --cflags --libs` -lGL -lGLU -lglut

clean:
	rm cv_gl_1 cv_gl_2