gistfile1.hpp

#include <SDL/SDL.h>
#include <SDL/SDL_thread.h>
#include <cmath>
#include <iostream>

using namespace std;

double scale = 1.0;
double x_offset = 0.0, y_offset = 0.0;

const double radius_sq = 4.0;
const int iterations = 500;
const double STEP_AMOUNT = 0.1;

int hue_offset = 180;
int value_offset = 0;
double saturation = 1.0;

double phi = 0.0;  // golden ratio - calculated in main()

void plot(SDL_Surface * surface, int x, int y, int i){
  double h = ((i+hue_offset) % 360);
  double s = saturation;
  double v = i == iterations ? 0.0 : 1.0;

  int hi = (int)(h / 60.0) % 6;
  double f = h / 60.0 - (int)(h / 60);
  double p = v * (1 - s);
  double q = v * (1 - f * s);
  double t = v * (1 - (1 - f) * s);

  double r, g, b;
  switch((int)hi){
  case 0:
    r = v;
    g = t;
    b = p;
    break;
  case 1:
    r = q;
    g = v;
    b = p;
    break;
  case 2:
    r = p;
    g = v;
    b = t;
    break;
  case 3:
    r = p;
    g = q;
    b = v;
    break;
  case 4:
    r = t;
    g = p;
    b = v;
    break;
  default:
    r = v;
    g = p;
    b = q;
    break;
  }
  
  *((Uint32*)surface->pixels + y * surface->w + x) =
    SDL_MapRGB(surface->format, (int)(r * 255), (int)(g * 255), (int)(b * 255));
}

void render(SDL_Surface * surface){
  int x, y;
  x = 0;
  int i;
  double x0, y0;
  double cr0, ci0;
  double rtemp;
  while (x < surface->w){
    y = 0;
    while (y < surface->h){
      x0 = ((double)x / (double)surface->w - 0.5) * scale * 2.0 + x_offset;
      y0 = ((double)y / (double)surface->h - 0.5) * scale * 2.0 + y_offset;
      i = 0;
      cr0 = -0.835;
      ci0 = -0.2321;
      while (x0*x0 + y0*y0 <= radius_sq && i < iterations){
        rtemp = x0*x0 - y0*y0 + cr0;
        y0 = 2*x0*y0 + ci0;
        x0 = rtemp;
        i++;
      }

      plot(surface, x, surface->h - y - 1, i);

      y++;
    }
    x++;
  }
  SDL_UpdateRect(surface, 0, 0, 0, 0);
}

int main(){
  phi = (1.0 + sqrt(5.0)) / 2.0;

  SDL_Init(SDL_INIT_VIDEO);

  SDL_Surface * wnd = SDL_SetVideoMode(800, 800, 32, SDL_HWSURFACE);

  bool loop = true;
  SDL_Event evt;

  render(wnd);

  while (loop){
    if (SDL_PollEvent(&evt)){
      switch(evt.type){
      case SDL_QUIT:
        loop = false;
        break;
      case SDL_KEYUP:
        switch(evt.key.keysym.sym){
        case SDLK_z:
          if ((evt.key.keysym.mod & KMOD_SHIFT) > 0){
            if (scale < 16.0)
              scale *= 2.0;
          }else{
            if (scale > 0.000030518)
              scale /= 2.0;
          }
          break;
        case SDLK_s:
          if ((evt.key.keysym.mod & KMOD_SHIFT) > 0){
            if (saturation < 1.0)
              saturation += 0.1;
          }else{
            if (saturation > 0.0)
              saturation -= 0.1;
          }
          break;
        case SDLK_h:
          if ((evt.key.keysym.mod & KMOD_SHIFT) > 0){
            hue_offset = (hue_offset + 10) % 360;
          }else{
            hue_offset = (hue_offset + 350) % 360;
          }
          break;
        case SDLK_LEFT:
          x_offset -= STEP_AMOUNT * scale;
          break;
        case SDLK_RIGHT:
          x_offset += STEP_AMOUNT * scale;
          break;
        case SDLK_DOWN:
          y_offset -= STEP_AMOUNT * scale;
          break;
        case SDLK_UP:
          y_offset += STEP_AMOUNT * scale;
          break;
        default:
          break;
        }
      default:
        break;
      }
    }
    hue_offset = (hue_offset + 1) % 360;
    render(wnd);
    SDL_Delay(1);
  }

  SDL_Quit();
}