CODEWITHSUNDEEP
copengltexturesglutframebuffer
PeterB
PeterB

Reputation: 2414

How to switch between textures/framebuffers on keypress using GLUT?

I have two buffers with .rgb images loaded. Original image is stored in frame_buffer and second one is stored in temp_buffer. I want to switch between those two images in GLUT window, when user press a button, how can I extend my code to do this?

typedef struct pixel{
    GLbyte r;
    GLbyte g;
    GLbyte b;
}Pixel;

Pixel frame_buffer[WIDTH][HEIGHT]; //original image
Pixel temp_buffer[WIDTH][HEIGHT]; //embossed image

GLuint texture;

int window_id;


void keyboardFunction(unsigned char button, int x, int y){
    switch(button){
        case 'S':
        case 's':
            // WHEN USER PRESS 'S', NEW IMAGE FROM temp_buffer IS
            // LOADED, HOW CAN I DO THIS?
            break;
        default:
            break;
    }
    glutPostRedisplay();
}


// Initialize OpenGL state
void init() {
    // Texture setup
    glEnable(GL_TEXTURE_2D);
    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

    // Other
    glClearColor(0, 0, 0, 0);
    gluOrtho2D(-1, 1, -1, 1);
    glLoadIdentity();
    glColor3f(1, 1, 1);

    loadInputFromUser();
    emboss();
}


void display() {
    // Copy frame_buffer to texture memory
    glBindTexture(GL_TEXTURE_2D, texture);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, WIDTH, HEIGHT, 0, GL_RGB, GL_UNSIGNED_BYTE, frame_buffer);
    // Clear screen buffer
    glClear(GL_COLOR_BUFFER_BIT);
    // Render a quad
    glBegin(GL_QUADS);
        glTexCoord2f(1, 0); glVertex2f(1, 1);
        glTexCoord2f(1, 1); glVertex2f(1, -1);
        glTexCoord2f(0, 1); glVertex2f(-1, -1);
        glTexCoord2f(0, 0); glVertex2f(-1, 1);
    glEnd();
    // Display result
    glFlush();
    //glutPostRedisplay();
    glutSwapBuffers();
}


// Main entry function
int main(int argc, char **argv) {

    // Init GLUT
    glutInit(&argc, argv);
    glutInitWindowPosition(-1, -1);
    glutInitWindowSize(WIDTH, HEIGHT);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutCreateWindow("Convolution Filter");
    // Set up OpenGL state
    init();
    // Run the control loop
    glutDisplayFunc(display);
    glutKeyboardFunc(keyboardFunction);
    glutReshapeFunc(changeViewPoint);

    GLenum err = glewInit();
    if (GLEW_OK != err){
        fprintf(stderr, "GLEW error");
        return 1;
    }
    glutMainLoop();
    return EXIT_SUCCESS;
}

  1. original image stored in frame_buffer

    enter image description here

  2. image filtered with emboss stored in temp_buffer (yeah I know its not perfect :D )

    enter image description here

I want to switch between them with keybutton.

Upvotes: 3

Views: 329

Answers (1)

Yakov Galka
Yakov Galka

Reputation: 72469

Edit the following snippets:

Pixel frame_buffer[WIDTH][HEIGHT]; //original image
Pixel temp_buffer[WIDTH][HEIGHT]; //embossed image
int which_image = 0;

...

    case 'S':
    case 's':
        which_image ^= 1;
        break;

...

glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, WIDTH, HEIGHT, 0, GL_RGB, GL_UNSIGNED_BYTE, which_image == 0 ? frame_buffer : temp_buffer);

...

glFlush();
glutPostRedisplay();
glutSwapBuffers();

That being said, you currently upload the texture (glTexImage2D) for each frame drawn. You should rather upload it only once during startup and each time it changes.

Upvotes: 3

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