#include <GL/glut.h>
#include <complex>

const char * title = "Mandelbrot set";
const double maxMod = 2.0;
const size_t maxIt = 1000;
const size_t maxX = 400;
const size_t maxY = 400;

int points[maxX][maxY];

std::complex<double> sqr(const std::complex<double> &v)
{
    return pow(v, 2);
}

void makeMandelbrotSet(void)
{
    for (int y = 0; y < maxY; ++y)
        for (int x = 0; x < maxX; ++x)
        {
            std::complex<double> z(0.0, 0.0);
            std::complex<double> c(1.0*(x-100) / 100, 1.0*(y-100) / 100);
            size_t i = 0;
            while (i < maxIt && abs(z) < maxMod)
            {
                z = sqr(z) + c;
                ++i;
            }
            if (abs(z) >= 2) points[y][x] = i;
            else points[y][x] = -1;
        }
}

void Resize(int width, int height)
{
    glutReshapeWindow(maxX, maxY);
}

void Draw(void)
{
    glClear(GL_COLOR_BUFFER_BIT);

    glBegin(GL_POINTS);
    for (int y = 0; y < maxY; ++y)
        for (int x = 0; x < maxX; ++x)
            if (points[y][x] != -1)
            {
                float col = (50.0 - points[y][x]) / 50.0;
                glColor3f(col, col, col);
                glVertex2f(x, y);
            }
    glEnd();
    glutSwapBuffers();
}

int main(int argc, char ** argv)
{
    glutInit(&argc, argv);

    makeMandelbrotSet();

    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(maxX, maxY);
    glutInitWindowPosition(200, 200);
    glutCreateWindow(title);

    glClearColor(0, 0, 0, 1.0);
    glPointSize(2);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, maxX/2, maxY/2, 0, -1, 1);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glutReshapeFunc(Resize);
    glutDisplayFunc(Draw);

    glutMainLoop();
    return EXIT_SUCCESS;
}