git.itanic.dy.fi Git - mandelbrot/blob - mandelbrot.c

   1 #include <SDL.h>
   2 #include <unistd.h>
   3 #include <stdio.h>
   4 #include <time.h>
   5 #include <string.h>
   6
   7 struct context {
   8         struct SDL_Surface *screen;
   9         double origo_x, origo_y;
  10         int motion_x, motion_y;
  11         double zoom;
  12         int scroll_enabled;
  13 };
  14
  15 static void putpixel(struct SDL_Surface *screen, const int x, const int y,
  16                      const unsigned char r, const unsigned char g,
  17                      const unsigned char b)
  18 {
  19         int offset = y * screen->pitch + x * 4;
  20         unsigned char *buf = screen->pixels;
  21
  22         buf[offset++] = b;
  23         buf[offset++] = g;
  24         buf[offset]   = r;
  25 }
  26
  27 #define MAX_ITERATION 1000
  28
  29 int get_mandelbrot_iterations(double x0, double y0)
  30 {
  31         double x = 0, y = 0, xtemp;
  32         int iteration = 0;
  33
  34         while ((x * x + y * y < 2 * 2) && iteration < MAX_ITERATION) {
  35
  36                 xtemp = x * x - y * y + x0;
  37                 y = 2 * x * y + y0;
  38
  39                 x = xtemp;
  40                 iteration++;
  41         }
  42
  43         return iteration;
  44 }
  45
  46 int draw_mandelbrot(struct SDL_Surface *screen, double x1, double x2,
  47                 double y1, double y2)
  48 {
  49         double x0, y0, xlen, ylen, xstep, ystep;
  50         int iteration, xs, ys;
  51
  52         printf("Drawing area (%f, %f)(%f, %f)\n", x1, y1, x2, y2);
  53
  54         xlen = x2 - x1;
  55         ylen = y2 - y1;
  56         xstep = xlen / (double)screen->w;
  57         ystep = ylen / (double)screen->h;
  58
  59         y0 = y1;
  60 #pragma omp parallel for private(xs, ys, x0, y0)
  61         for (ys = 0; ys < screen->h; ys++) {
  62                 y0 = y1 + ystep * ys;
  63                 x0 = x1;
  64                 for (xs = 0; xs < screen->w; xs++) {
  65                         iteration = get_mandelbrot_iterations(x0, y0);
  66
  67                         if (iteration == MAX_ITERATION)
  68                                 putpixel(screen, xs, ys, 255, 255, 255);
  69                         else
  70                                 putpixel(screen, xs, ys,
  71                                         iteration * 8, iteration,
  72                                         iteration / 4);
  73                         x0 += xstep;
  74                 }
  75         }
  76
  77         SDL_Flip(screen);
  78         return 0;
  79 }
  80
  81 static int read_events(struct context *ctx)
  82 {
  83         SDL_Event event;
  84         int wait = 1, ret, exit = 0, delayed_exit = 0;
  85
  86         while (!exit) {
  87                 if (wait) {
  88                         SDL_WaitEvent(&event);
  89                         wait = 0;
  90                 } else {
  91                         ret = SDL_PollEvent(&event);
  92                         if (!ret) {
  93                                 wait = 1;
  94                                 exit = delayed_exit;
  95                         }
  96                 }
  97
  98                 switch (event.type) {
  99                 case SDL_KEYDOWN:
 100                         switch (event.key.keysym.sym) {
 101                         case SDLK_ESCAPE:
 102                                 goto quit;
 103                         default:
 104                                 break;
 105                         }
 106                         break;
 107                 case SDL_KEYUP:
 108                         switch (event.key.keysym.sym) {
 109                         default:
 110                                 break;
 111                         }
 112                         break;
 113                 case SDL_MOUSEBUTTONDOWN:
 114                         if (event.button.button == 4) {
 115                                 ctx->zoom *= 1.5;
 116                                 exit++;
 117                         } else if (event.button.button == 5) {
 118                                 ctx->zoom /= 1.5;
 119                                 delayed_exit++;
 120                         } else {
 121                                 ctx->scroll_enabled = 1;
 122                         }
 123                         break;
 124                 case SDL_MOUSEBUTTONUP:
 125                         ctx->scroll_enabled = 0;
 126                         exit++;
 127                         break;
 128                 case SDL_MOUSEMOTION:
 129                         if (!ctx->scroll_enabled)
 130                                 break;
 131
 132                         ctx->motion_x -= event.motion.xrel;
 133                         ctx->motion_y -= event.motion.yrel;
 134                         delayed_exit++;
 135                         break;
 136                 case SDL_VIDEORESIZE:
 137                         ctx->screen =
 138                                 SDL_SetVideoMode(event.resize.w,
 139                                                  event.resize.h,
 140                                                  32,
 141                                                  ctx->screen->flags);
 142                         exit++;
 143                         break;
 144                 case SDL_QUIT:
 145                         goto quit;
 146                 }
 147         }
 148
 149         return 0;
 150 quit:
 151         printf("\nExiting. Good bye!\n");
 152         return 1;
 153 }
 154
 155 static void loop(struct context *ctx)
 156 {
 157         double aspect_ratio;
 158
 159         do {
 160                 aspect_ratio = ctx->screen->w / ctx->screen->h;
 161                 ctx->origo_x += ctx->motion_x / ctx->zoom / ctx->screen->w;
 162                 ctx->origo_y += ctx->motion_y / ctx->zoom / ctx->screen->h;
 163                 ctx->motion_x = ctx->motion_y = 0;
 164
 165                 draw_mandelbrot(ctx->screen,
 166                                 ctx->origo_x - aspect_ratio / ctx->zoom,
 167                                 ctx->origo_x + aspect_ratio / ctx->zoom,
 168                                 ctx->origo_y - 1 / ctx->zoom,
 169                                 ctx->origo_y + 1 / ctx->zoom);
 170         } while (!read_events(ctx));
 171 }
 172
 173 int main(int argc, char *argv[])
 174 {
 175         struct context ctx;
 176         int flags = SDL_DOUBLEBUF | SDL_HWSURFACE | SDL_RESIZABLE;
 177         int xres = 800, yres = 600;
 178
 179         memset(&ctx, 0, sizeof(ctx));
 180         ctx.zoom = 1;
 181
 182         if (SDL_Init(SDL_INIT_VIDEO) != 0) {
 183                 fprintf(stderr, "Unable to initialize SDL: %s\n",
 184                         SDL_GetError());
 185
 186                 return 1;
 187         }
 188         atexit(SDL_Quit);
 189
 190         ctx.screen = SDL_SetVideoMode(xres, yres, 32, flags);
 191         if (ctx.screen == NULL) {
 192                 fprintf(stderr, "Unable to set video mode: %s\n",
 193                         SDL_GetError());
 194                 return 2;
 195         }
 196
 197         SDL_WM_SetCaption(argv[0], NULL);
 198
 199         loop(&ctx);
 200
 201         return 0;
 202 }