add mandelbrot

mandelbrot.c

@@ -0,0 +1,54 @@
+#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(640, 480, 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;
+
+    if (x == 0) {
+      printf("y = %d\n", y);
+    }
+
+    float complex c =     (3.0 * x / 640.0) - 2.0
+                    + I * ((2.0 * y / 480.0) - 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 = 0x00000000;
+    if (diverges) {
+      color = 0x01010101 * it;
+    }
+
+    pixels[i] = color;
+  }
+  if (SDL_MUSTLOCK(screen)) {
+    SDL_UnlockSurface(screen);
+  }
+  SDL_Flip(screen);            /* XXX */
+
+  SDL_Delay(20000);
+
+  SDL_Quit();
+}