opengl_opencv_example/main.cpp

#include <opencv2/core.hpp>
#include <opencv2/core/opengl.hpp>
#include <opencv2/imgcodecs.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui.hpp>
 
#include <iostream>

#ifdef __APPLE__
    #include <OpenGL/gl.h>
    #include <OpenGL/gl3.h>
    #include <GLUT/glut.h>
#else
    #include <GL/glew.h>
    #include <GL/glut.h>
#endif

using namespace cv;
using namespace std;
using namespace std::chrono;
using time_stamp = time_point<system_clock, microseconds>;

GLuint imageTexture;
GLint screenWidth = 0;
GLint screenHeight = 0;
time_stamp ts;

/**
 * rows = height
 * cols = width
 **/
void loadTexture (GLuint& imageTexture1)
{
  string image_path = samples::findFile("chart.png");
  Mat loaded = imread(image_path, IMREAD_COLOR);
  Mat image = Mat::zeros(screenHeight, screenWidth, CV_8UC3);
  //Mat resized = Mat::zeros(1080, 1280, CV_8UC3)
  cout << "created image" << endl;
  if (image.empty()) {
      cout << "image empty" << endl;
  } else {
      cout << "loaded " << image_path << endl;
      cout << "   dim " << loaded.cols << "x" << loaded.rows << endl;

      //resize(loaded, resized, Size(1280, 1080));
      cout << " image " << image.cols << "x" << image.rows << endl;
      //cout << "resized " << resized.cols << "x" << resized.rows << endl;
      //resized.copyTo(image(Rect(0, 0, resized.cols, resized.rows)));
      uint32_t offsetX = (image.cols - loaded.cols) >> 1;
      uint32_t offsetY = (image.rows - loaded.rows) >> 1;
      loaded.copyTo(image(Rect(offsetX, offsetY, loaded.cols, loaded.rows)));
      flip(image, image, 0);

#if (CV_VERSION_MAJOR >= 4)
      cvtColor(image, image, cv::COLOR_BGR2RGB);
#else
      cvtColor(image, image, CV_BGR2RGB);
#endif
      glGenTextures(1, &imageTexture1);
      glBindTexture(GL_TEXTURE_2D, imageTexture1);

      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

      glTexImage2D(GL_TEXTURE_2D,            // Type of texture
                        0,                   // Pyramid level (for mip-mapping) - 0 is the top level
                        GL_RGB,              // Internal colour format to convert to
                        image.cols,          // Image width  i.e. 640 for Kinect in standard mode
                        image.rows,          // Image height i.e. 480 for Kinect in standard mode
                        0,                   // Border width in pixels (can either be 1 or 0)
                        GL_RGB,              // Input image format (i.e. GL_RGB, GL_RGBA, GL_BGR etc.)
                        GL_UNSIGNED_BYTE,    // Image data type
                        image.ptr());        // The actual image data itself
    cout << "display()" << endl;
    }
}

void getScreenDimensions ()
{
  if (screenWidth == 0 && screenHeight == 0) {
    GLint dims[4] = {0};
    glGetIntegerv(GL_VIEWPORT, dims);
    screenWidth = dims[2];
    screenHeight = dims[3];
    cout << screenWidth << "," << screenHeight << endl;
  }
}
 
void display(void)
{
  getScreenDimensions();
  loadTexture(imageTexture);
  ts = time_point_cast<microseconds>(system_clock::now());
  
  glClear(GL_COLOR_BUFFER_BIT);
  glEnable(GL_TEXTURE_2D);
  glViewport(0, 0, screenWidth, screenHeight);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);
  glBindTexture(GL_TEXTURE_2D, imageTexture);

  glBegin(GL_QUADS);  // front face
    glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 0.0f);  //bottom right
    glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, 0.0f);   //top right
    glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, 0.0f);  //top left
    glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 0.0f); //bottom left
  glEnd();
  glDisable(GL_TEXTURE_2D);
  glBindTexture(GL_TEXTURE_2D, 0);
  glutSwapBuffers();

  //glFlush();
}
 
int main(int argc, char** argv)
{
    if (argc > 1)
    {
        screenWidth = atoi(argv[1]);
        cout << "Set width: " << screenWidth << endl;
    }
    if (argc > 2)
    {
        screenHeight = atoi(argv[2]);
        cout << "Set height: " << screenHeight << endl;
    }
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE);
    glutCreateWindow("opengl_opencv_example");
    glutFullScreen();
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}