Digital Differential Analyzer (DDA) Algorithm

/*************************************************
* Digital Differential Analyzer (DDA) Algorithm *
*************************************************
* Usage    :- Simple and general method for rasterizing lines and triangles
* Author   :- Rooparam Choudhary
* Date     :- August 29, 2009
* Place    :- Shri Mata Vaishno Devi University
* EntryNo  :- 2006ECS20
*/

#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <iostream>

#define ROUND(x) ((int)(x+0.5))

int    MYCOLOR = WHITE;

inline void setpixel(int, int);
void DDA(int, int, int, int);
void unionJack(void);
void hexagon(int, int);
void randomUnionJack(int);

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

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 DDA(int x0, int y0, int x1, int y1) {
  int delX = x1-x0, delY = y1-y0, steps, k;
  float x=x0, y=y0, incX, incY;

  steps = (abs(delX) > abs(delY)) ? abs(delX) : abs(delY) ;

  incX = delX / (float)steps;
  incY = delY / (float)steps;

  setpixel(ROUND(x), ROUND(y));
  for(k=0; k<steps; ++k) {
      x += incX;
      y += incY;
      setpixel(ROUND(x), ROUND(y));
  }
}

int main(void) {
  int gd = DETECT, gm;
  char *author = "Coder:- Rooparam Choudhary";
  char *algo = "Digital Differential Analyzer Algorithm";
  char point[30];
  std::cout << "Digital Differential Analyzer Algorithm\n";
  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);

  MYCOLOR = GREEN;
  // X-axis
  DDA(-320, -1, 320, -1);
  DDA(-320,  0, 320,  0);
  DDA(-320,  1, 320,  1);
  // Y-axis
  DDA(-1, 240, -1, -240);
  DDA( 0, 240,  0, -240);
  DDA( 1, 240,  1, -240);
  // Y - X = 0
  DDA(-240, -240, 240, 240);
  // Y + X = 0
  DDA(-240, 240, 240, -240);

  MYCOLOR = BROWN;
  hexagon(-160, 120);
  hexagon(160, 120);
  hexagon(160, -120);
  hexagon(-160, -120);

  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);

  int x0, y0, x1, y1;
  MYCOLOR = WHITE;
  std::cout << "Enter \'-400\' to exit\n";
  std::cout << "Enter the coordinates of end points: [x0 y0 x1 y1]\n";

  std::cin >> x0;
  while(x0 != -400) {
      std::cin >> y0 >> x1 >> y1;
      sprintf(point, "(%4d, %4d)", x0, y0);
      outtextxy(320+x0-textwidth(point)/2, 240-y0+2, point);
      sprintf(point, "(%4d, %4d)", x1, y1);
      outtextxy(320+x1-textwidth(point)/2, 240-y1+2, point);
      DDA(x0, y0, x1, y1);

      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 >> x0;
  }

  closegraph();
  return 0;
}

void unionJack(void){
  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); }
  }
}

void hexagon(int xc, int yc) {
  DDA(xc+60, yc+104, xc+120, yc);
  DDA(xc+60, yc+104, xc+60, yc-104);
  DDA(xc+60, yc+104, xc-60, yc-104);
  DDA(xc+60, yc+104, xc-120, yc);
  DDA(xc+60, yc+104, xc-60, yc+104);
  DDA(xc+120, yc, xc+60, yc-104);
  DDA(xc+120, yc, xc-60, yc-104);
  DDA(xc+120, yc, xc-120, yc);
  DDA(xc+120, yc, xc-60, yc+104);
  DDA(xc+60, yc-104, xc-60, yc-104);
  DDA(xc+60, yc-104, xc-120, yc);
  DDA(xc+60, yc-104, xc-60, yc+104);
  DDA(xc-60, yc-104, xc-120, yc);
  DDA(xc-60, yc-104, xc-60, yc+104);
  DDA(xc-120, yc, xc-60, yc+104);
}