c-exercises/mandelbrot.c

#include "SDL.h"
#include <complex.h>
#include <stdbool.h>

int main(int argc, char *argv[]) {
  SDL_Surface *screen = NULL;
  if (SDL_Init(SDL_INIT_EVERYTHING) < 0) {
    printf("Error: Could not initialize SDL: %s.\n", SDL_GetError());
    exit(1);
  }
  screen = SDL_SetVideoMode(1280, 800, 32, SDL_SWSURFACE);

  if (SDL_MUSTLOCK(screen)) {
    SDL_LockSurface(screen);
  }
  Uint32 *pixels = (Uint32 *) screen->pixels;
  for (int i = 0; i < screen->w * screen->h; i++) {
    int y = i / screen->w;
    int x = i % screen->w;

    float complex c = ((3.0 * x / screen->w) - 2.0)
        + I * ((2.0 * y / screen->h) - 1.0);

    bool diverges = false;
    float complex z = 0;
    int it;
    for (it = 1; it < 256; it++) {
      z = cpowf(z, 2) + c;
      if (cabs(z) > 100) {
        diverges = true;
        break;
      }
    }

    Uint32 color;
    if (diverges) {
      color = 0x00010001 * it;
    } else {
      color = 0x00000000;
    }

    pixels[i] = color;
    if (y % 10 == 0)
      SDL_Flip(screen);
  }

  /* Save BMP */
  char *file = "mandelbrot.bmp";
  if (SDL_SaveBMP(screen, file) != 0) {
    fprintf(stderr, "Could not write %s!\n", file);
  }

  if (SDL_MUSTLOCK(screen)) {
    SDL_UnlockSurface(screen);
  }
  SDL_Flip(screen);

  SDL_Delay(20000);

  SDL_Quit();
}