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         xlen = x2 - x1;
  53         ylen = y2 - y1;
  54         xstep = xlen / (double)screen->w;
  55         ystep = ylen / (double)screen->h;
  56
  57         y0 = y1;
  58 #pragma omp parallel for private(xs, ys, x0, y0)
  59         for (ys = 0; ys < screen->h; ys++) {
  60                 y0 = y1 + ystep * ys;
  61                 x0 = x1;
  62                 for (xs = 0; xs < screen->w; xs++) {
  63                         iteration = get_mandelbrot_iterations(x0, y0);
  64
  65                         if (iteration == MAX_ITERATION)
  66                                 putpixel(screen, xs, ys, 255, 255, 255);
  67                         else
  68                                 putpixel(screen, xs, ys,
  69                                         iteration * 8, iteration,
  70                                         iteration / 4);
  71                         x0 += xstep;
  72                 }
  73         }
  74
  75         SDL_Flip(screen);
  76         return 0;
  77 }
  78
  79 static int read_events(struct context *ctx)
  80 {
  81         SDL_Event event;
  82         int wait = 1, ret, exit = 0, delayed_exit = 0;
  83
  84         while (!exit) {
  85                 if (wait) {
  86                         SDL_WaitEvent(&event);
  87                         wait = 0;
  88                 } else {
  89                         ret = SDL_PollEvent(&event);
  90                         if (!ret) {
  91                                 wait = 1;
  92                                 exit = delayed_exit;
  93                         }
  94                 }
  95
  96                 switch (event.type) {
  97                 case SDL_KEYDOWN:
  98                         switch (event.key.keysym.sym) {
  99                         case SDLK_ESCAPE:
 100                                 goto quit;
 101                         default:
 102                                 break;
 103                         }
 104                         break;
 105                 case SDL_KEYUP:
 106                         switch (event.key.keysym.sym) {
 107                         default:
 108                                 break;
 109                         }
 110                         break;
 111                 case SDL_MOUSEBUTTONDOWN:
 112                         if (event.button.button == 4) {
 113                                 ctx->zoom *= 1.5;
 114                                 exit++;
 115                         } else if (event.button.button == 5) {
 116                                 ctx->zoom /= 1.5;
 117                                 delayed_exit++;
 118                         } else {
 119                                 ctx->scroll_enabled = 1;
 120                         }
 121                         break;
 122                 case SDL_MOUSEBUTTONUP:
 123                         ctx->scroll_enabled = 0;
 124                         exit++;
 125                         break;
 126                 case SDL_MOUSEMOTION:
 127                         if (!ctx->scroll_enabled)
 128                                 break;
 129
 130                         ctx->motion_x -= event.motion.xrel;
 131                         ctx->motion_y -= event.motion.yrel;
 132                         delayed_exit++;
 133                         break;
 134                 case SDL_VIDEORESIZE:
 135                         ctx->screen =
 136                                 SDL_SetVideoMode(event.resize.w,
 137                                                  event.resize.h,
 138                                                  32,
 139                                                  ctx->screen->flags);
 140                         exit++;
 141                         break;
 142                 case SDL_QUIT:
 143                         goto quit;
 144                 }
 145         }
 146
 147         return 0;
 148 quit:
 149         printf("\nExiting. Good bye!\n");
 150         return 1;
 151 }
 152
 153 static void loop(struct context *ctx)
 154 {
 155         double aspect_ratio;
 156
 157         do {
 158                 aspect_ratio = ctx->screen->w / ctx->screen->h;
 159                 ctx->origo_x += ctx->motion_x / ctx->zoom / ctx->screen->w;
 160                 ctx->origo_y += ctx->motion_y / ctx->zoom / ctx->screen->h;
 161                 ctx->motion_x = ctx->motion_y = 0;
 162
 163                 draw_mandelbrot(ctx->screen,
 164                                 ctx->origo_x - aspect_ratio / ctx->zoom,
 165                                 ctx->origo_x + aspect_ratio / ctx->zoom,
 166                                 ctx->origo_y - 1 / ctx->zoom,
 167                                 ctx->origo_y + 1 / ctx->zoom);
 168                 printf("Drawing area (%f, %f)(%f, %f), zoom %d\n",
 169                         x1, y1, x2, y2, 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 }