OpenGL/Framebuffer

#include <GL/glew.h>
#include <GL/glut.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <string>
#include <list>
#include <vector>
#include <unistd.h>

void display();
void idle();
void resize(int w, int h);
void keyboardEvent(unsigned char key, int x, int y);
void init();

GLuint framebuffername;
GLuint texturename;
GLuint renderbuffername;
GLuint color;
cv::Mat image;
int windowWidth, windowHeight;

GLfloat triangle[] = {
    100.0f, 100.0f, 0.0f, 100.0f/1440.0f, 100.0f/1080.0f,
    500.0f, 900.0f, 0.0f, 500.0f/1440.0f, 900.0f/1080.0f,
    1000.0f, 800.0f, 0.0f, 1000.0f/1440.0f, 800.0f/1080.0f
};

GLuint tvbo;


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

    if(argc < 2) return 1;

    std::string filename = argv[1];

    image = cv::imread(filename.c_str(), CV_LOAD_IMAGE_COLOR);

    std::cout << image.rows << " " << image.cols << " " << image.step << " " << image.dataend-image.datastart << " " << image.cols*image.rows*3 << std::endl;

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB );
    glutInitWindowSize(image.cols, image.rows);
    glutCreateWindow("Test");

    glutReshapeFunc(resize);
    glutDisplayFunc(display);
    glutIdleFunc(idle);
    glutKeyboardFunc(keyboardEvent);

    glewExperimental = GL_TRUE;
    GLenum glewerr = glewInit();
    if(GLEW_OK != glewerr) {
        std::cerr << glewGetErrorString(glewerr) << std::endl;
    }

    init();
    glutMainLoop();

    return 0;
}

void init() {
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

    framebuffername = 0;
    glGenFramebuffers(1, &framebuffername);
    glBindFramebuffer(GL_FRAMEBUFFER, framebuffername);

    texturename = 0;
    glGenTextures(1, &texturename);
    glBindTexture(GL_TEXTURE_2D, texturename);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, image.cols, image.rows, 0, GL_RGB, GL_UNSIGNED_BYTE, image.data);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

    glBindTexture(GL_TEXTURE_2D, 0);

    color = 0;
    glGenTextures(1, &color);
    glBindTexture(GL_TEXTURE_2D, color);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, image.cols, image.rows, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, color, 0);

    glBindTexture(GL_TEXTURE_2D, 0);
    glBindFramebuffer(GL_FRAMEBUFFER, 0);

    renderbuffername = 0;
    glGenRenderbuffers(1, &renderbuffername);
    /*glBindRenderbuffer(GL_RENDERBUFFER, renderbuffername);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_RGB, image.cols, image.rows);
    glBindFramebuffer(GL_FRAMEBUFFER, framebuffername);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderbuffername);*/

    //glGenBuffers(1, &tvbo);
    //glBindBuffer(GL_ARRAY_BUFFER, tvbo);
    //glBufferData(GL_ARRAY_BUFFER, sizeof(triangle), triangle, GL_STATIC_DRAW);
}

void display() {

    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, texturename);
    glBindFramebuffer(GL_FRAMEBUFFER, framebuffername);

    if(GL_FRAMEBUFFER_COMPLETE == glCheckFramebufferStatus(GL_FRAMEBUFFER)) {
    } else std::cout << "Framebuffer is NOT complete" << std::endl;

    glPushAttrib(GL_VIEWPORT_BIT);
    glViewport(0, 0, image.cols, image.rows);

    glClear(GL_COLOR_BUFFER_BIT);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, image.cols, image.rows, 0, -1, 1);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glBegin(GL_TRIANGLES);
    glTexCoord2f(100.0f/image.cols, 100.0f/image.rows);
    glVertex3i(100, 100, 0);
    glTexCoord2f(500.0f/image.cols, 900.0f/image.rows);
    glVertex3i(500, 900, 0);
    glTexCoord2f(1000.0f/image.cols, 800.0f/image.rows);
    glVertex3i(1000, 800, 0);
    glEnd();
    glFlush();
    glPopAttrib();

    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    glBindTexture(GL_TEXTURE_2D, 0);

    std::fill(image.datastart, image.dataend, 0);
    glReadBuffer(GL_COLOR_ATTACHMENT0);
    glReadPixels(0, 0, image.cols, image.rows, GL_RGB, GL_UNSIGNED_BYTE, image.data);
    glutSwapBuffers();
}

void idle() {
    glutPostRedisplay();
}

void resize(int w, int h) {
    windowWidth = w;
    windowHeight = h;
    glutPostRedisplay();
}

void keyboardEvent(unsigned char key, int x, int y) {
    (void)x;
    (void)y;
    if(27 == key) {
        //glReadPixels(0, 0, image.cols, image.rows, GL_RGB, GL_UNSIGNED_BYTE, image.data);
        //std::fill(image.datastart, image.dataend, 0);

        cv::imwrite("./output.jpg", image);

        glDeleteBuffers(1, &framebuffername);
        glDeleteBuffers(1, &renderbuffername);
        glDeleteBuffers(1, &texturename);
        glDeleteBuffers(1, &color);
        exit(0);
    }
    return;
}