#include <cstdlib>

#include <cstdint>

#include <cassert>

#include <complex>

#ifdef WIN32

#include <SDL.h>

#else

#include <SDL/SDL.h>

#endif

using namespace std;

struct sdl_error {};

inline void sdl_check(bool allclear) { if (!allclear) throw sdl_error(); }

inline void put_pixel(SDL_Surface* screen, int x, int y, uint32_t pixel)

{

assert(screen->format->BytesPerPixel == 4);

auto pixel_address= reinterpret_cast<uint32_t*>(screen->pixels) + y * screen->w + x;

*pixel_address= pixel;

}

class mandel_pixel

{

public:

mandel_pixel(SDL_Surface* screen, int x, int y, int xdim, int ydim, int max_iter)

: screen(screen), max_iter(max_iter), iter(0), c(x, y)

{

// scale y to [-1.2,1.2] and shift -0.5+0i to the center

c*= 2.4f / static_cast<float>(ydim);

c-= complex<float>(1.2 * xdim / ydim + 0.5, 1.2);

iterate();

}

int iterations() const { return iter; }

uint32_t color() const

{

if (iter == max_iter) return SDL_MapRGB(screen->format, 0, 0, 0);

const int ci= 512 * iter / max_iter; // incremental value for color

// return SDL_MapRGB(screen->format, 40*iter & 255, 66*iter & 255, 100*iter & 255);

return iter < max_iter/2 ? SDL_MapRGB(screen->format, ci, 0, 0)

: SDL_MapRGB(screen->format, 255, ci-255, ci-255);

}

private:

void iterate()

{

complex<float> z= c;

for (; iter < max_iter && norm(z) <= 4.0f; iter++)

z= z * z + c;

};

SDL_Surface* screen;

const int max_iter;

int iter;

complex<float> c;

};

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

{

const int max_iter= 30;

int xdim= 1200, ydim= 800;

if (argc >= 3)

xdim= atoi(argv[1]), ydim= atoi(argv[2]);

sdl_check(SDL_Init(SDL_INIT_VIDEO) != -1);

SDL_Surface* screen = SDL_SetVideoMode(xdim, ydim, 32, SDL_DOUBLEBUF); sdl_check(screen);

SDL_WM_SetCaption("Mandelbrot's Apple Manikin", "Mandelbrot's Apple Manikin");

SDL_LockSurface(screen);

for (int y= 0; y < ydim; y++)

for (int x= 0; x < xdim; x++) {

mandel_pixel m(screen, x, y, xdim, ydim, max_iter);

put_pixel(screen, x, y, m.color());

}

SDL_UnlockSurface(screen);

SDL_Flip(screen);

// SDL_SaveBMP(screen, "mandelbrot.bmp"); // if you want to save the fractal

bool run = true;

while(run) {

// Polling for events as long as there exists some

SDL_Event event;

while(SDL_PollEvent(&event))

switch(event.type) {

case SDL_QUIT: run = false; break;

}

}

SDL_Quit();

}