Simple Circle Drawing Algorithm

/*************************************************
* Simple Circle Drawing Algorithm               *
*************************************************
* Usage    :- Simple and general method for rasterizing circles
* Author   :- Rooparam Choudhary
* Date     :- August 29, 2009 [12:40 PM IST]
* Place    :- Shri Mata Vaishno Devi University
* EntryNo  :- 2006ECS20
*/

#include <graphics.h>
#include <stdlib.h>
#include <iostream>
#include <math.h>
#include <time.h>

#define ROUND(x) ((x>0)?(int)(x+0.5):(int)(x-0.5))
#define PI       3.14159265

inline void setpixel(int, int);
void unionJack(void);
void simpleCircle(float, float, float);
inline void draw(float, float, float, float);
void wait(void);
void randomUnionJack(int);

int MYCOLOR =    WHITE;
clock_t DELAY = 0;

void randomUnionJack(int count){
    void DJ(int, int, int);
    int xr, yr, clr=0;
    srand(time(NULL));
   
    while(count-- > 0){
                  xr = -320 + rand()%641;
                  yr = -240 + rand()%481;
                  clr = 0;
                  if(yr > -xr){
                        if(xr < 0)        clr = 3;
                        else if(yr < 0)   clr = 2;
                        else if(yr > xr)  clr = 4;
                        else if(yr < xr)  clr = 1;
                  }else if(yr < -xr) {
                        if(xr > 0)        clr = 3;
                        else if(yr > 0)   clr = 2;
                        else if(yr < xr)  clr = 4;
                        else if(yr > xr)  clr = 1;
                  }
                  DJ(xr, yr, clr);
    }
}

void DJ(int x, int y, int clr){
    int shade = 0;
    switch(clr){
    case 1:     shade = RED;        break;
    case 2:     shade = BLUE;       break;
    case 3:     shade = CYAN;       break;
    case 4:     shade = MAGENTA;    break;
    default:    return;             break;
    }
    putpixel(320+x, 240-y, shade);
}

void wait(void) {
    clock_t init = clock();
    while( (clock() - init) < DELAY)
           ;
}

/* Circle drawing algorithm */
void simpleCircle(float xc, float yc, float radius) {
    float step = 1.0f / radius,  theta = 0.0f;
    float x = radius,       y = 0.0f;
    do{
          draw(xc, yc, x, y);
          theta += step;
          x = radius*cos(theta);
          y = radius*sin(theta);
          wait();
    }while(theta <= PI / 4.0f);
}

/* Using the symmetry of Circle to draw points in other octants */
inline void draw(float xc, float yc, float x, float y) {
    setpixel(ROUND(xc+x), ROUND(yc+y));      // Ist      Octant
    setpixel(ROUND(xc+y), ROUND(yc+x));      // IInd     Octant
    setpixel(ROUND(xc-y), ROUND(yc+x));      // IIIrd    Octant
    setpixel(ROUND(xc-x), ROUND(yc+y));      // IVth     Octant
    setpixel(ROUND(xc-x), ROUND(yc-y));      // Vth      Octant
    setpixel(ROUND(xc-y), ROUND(yc-x));      // VIth     Octant
    setpixel(ROUND(xc+y), ROUND(yc-x));      // VIIth    Octant
    setpixel(ROUND(xc+x), ROUND(yc-y));      // VIIIth   Octant
}

inline void setpixel(int x, int y){
      putpixel(320+x, 240-y, MYCOLOR);
}

void unionJack(){
   for(int y = 240; y>0; --y) {
           int x = -321;

           MYCOLOR = BLUE;
           while(++x < -y)
               { putpixel(320+x, 240-y, MYCOLOR); }
           MYCOLOR = CYAN;
           while(++x < 0)
               { putpixel(320+x, 240-y, MYCOLOR); }          
           MYCOLOR = MAGENTA;
           while(++x < y)
               { putpixel(320+x, 240-y, MYCOLOR); }
           MYCOLOR = RED;
           while(++x < 321)
               { putpixel(320+x, 240-y, MYCOLOR); }
   }
   for(int y = -1; y>-241; --y) {
           int x = -321;

           MYCOLOR = RED;
           while(++x < y)
               { putpixel(320+x, 240-y, MYCOLOR); }
           MYCOLOR = MAGENTA;
           while(++x < 0)
               { putpixel(320+x, 240-y, MYCOLOR); }
           MYCOLOR = CYAN;
           while(++x < -y)
               { putpixel(320+x, 240-y, MYCOLOR); }
           MYCOLOR = BLUE;
           while(++x < 321)
               { putpixel(320+x, 240-y, MYCOLOR); }
   }
}

int main(void) {
   int gd = DETECT, gm;
   char *author = "Coder:- Rooparam Choudhary";
   char *algo = "Simple Circle Drawing Algorithm";
   char point[30];
   std::cout << algo << std::endl;
   std::cout << author << std::endl;
   initgraph(&gd, &gm, "C:\\");
  
   setcolor(WHITE);
   setbkcolor(GREEN);
   outtextxy(320 - textwidth(algo)/2, 5, algo);
   outtextxy(getmaxx()-4 -textwidth(author), getmaxy()-20, author);
   setcolor(GREEN);
   setbkcolor(BLACK);
  
   setcolor(YELLOW);
   // X-axis
   line(0, 239, 640, 239);
   line(0, 240, 640, 240);
   line(0, 241, 640, 241);
   // Y-axis
   line(319, 0, 319, 480);
   line(320, 0, 320, 480);
   line(321, 0, 321, 480);
   // Y + X = 0
   line(80, 0, 560, 480);
   // Y - X = 0
   line(80, 480, 560, 0);

   std::cout << "Enter samples for union jack\n(SHOULD BE GEATER THAN 100K): ";
   int samp;
   std::cin >> samp;
   //unionJack();
   randomUnionJack(samp);

   setcolor(WHITE);
   setbkcolor(GREEN);
   outtextxy(320 - textwidth(algo)/2, 5, algo);
   outtextxy(getmaxx()-4 -textwidth(author), getmaxy()-20, author);
   setcolor(GREEN);
   setbkcolor(BLACK);

   float xc, yc, r;
  
   MYCOLOR = WHITE;
   std::cout << "Enter \'-400\' to exit\n";
   std::cout << "Enter Delay: ";
   std::cin >> DELAY;
   std::cout << "Enter the coordinates of circle center and it's radius: [xc yc r]\n";

   std::cin >> xc;
   while((int)xc != (int)-400.0f ) {
       std::cin >> yc >> r;
       sprintf(point, "(%4.1f, %4.1f) %4.1f", xc, yc, r);
       setpixel(ROUND(xc), ROUND(yc));
       line(320+ROUND(xc), 240-ROUND(yc), 320+ROUND(xc+r), 240-ROUND(yc));
       outtextxy(320+ROUND(xc)-textwidth(point)/2, 240-ROUND(yc)+2, point);
       simpleCircle(xc, yc, r);

       setcolor(WHITE);
       setbkcolor(GREEN);
       outtextxy(320 - textwidth(algo)/2, 5, algo);
       outtextxy(getmaxx()-4 -textwidth(author), getmaxy()-20, author);
       setcolor(GREEN);
       setbkcolor(BLACK);

       std::cin >> xc;
   }

   closegraph();
   return 0;
}