How to draw an image from a 2d array in modern openGL

Question

I want to draw points with openGL, I have a 32x32 screen size and I want to fill it with the color red, however I don't understand how the parameters of glVertex2f(-1, 0.5) are working

My first instinct was to do something like this:

glutInit(&argc, argv);                 // Initialize GLUT
glutCreateWindow("OpenGL Setup Test"); // Create a window with the given title
glutInitWindowSize(32, 32);   // Set the window's initial width & height
glutDisplayFunc(displaySpectrogram); // Register display callback handler for window re-paint
glutMainLoop();           // Enter the event-processing loop

glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Set background color to black and opaque
glClear(GL_COLOR_BUFFER_BIT);         // Clear the color buffer (background)

glBegin(GL_POINTS);              
glColor3f(1.0f, 0.0f, 0.0f); // Red
for (int i = 0; i < 32; i++)
{
    for (int j = 0; j < 32; j++)
    {
        glVertex2f(i,j);
    }
}
glEnd();

glFlush();  // Render now

But glVertex2f() parameters range is -1 to 1 I think so I'm not sure how to achieve that.

There is another way with texture but I have no idea on how to use them and there are no tutorials for that online

Answer 1

I recommend to use an Orthographic projection . In Orthographic Projection, the view space coordinates are linearly mapped to the clip space coordinates and normalized device coordinates. The viewing volume is defined by 6 distances (left, right, bottom, top, near, far). The values for left, right, bottom, top, near and far define a cuboid (box).
With legacy OpenGL matrices you can use glOrtho to set an orthographic projection matrix:

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, 32, 0, 32, -1, 1);