CG_practical2_concave_polygon.cpp

/* 1. Write C++ program to draw a concave polygon and fill it with desired color
using scan fill algorithm. Apply the concept of inheritance.  */

#include <conio.h>
#include <iostream>
#include <graphics.h>
#include <stdlib.h>
using namespace std;
class point
{
public:
   int x, y;
};
class poly
{
private:
   point p[20];
   int inter[20], x, y;
   int v, xmin, ymin, xmax, ymax;

public:
   int c;
   void read();
   void calcs();
   void display();
   void ints(float);
   void sort(int);
};
void poly::read()
{
   int i;
   cout << "\n Scan Fill Algorithm ";
   cout << "\n Enter Number Of Vertices Of Polygon: ";
   cin >> v;
   if (v > 2)
   {
      for (i = 0; i < v; i++) // ACCEPT THE VERTICES
      {
         cout << "\nEnter co-ordinate no. " << i + 1 << " : ";
         cout << "\n\tx" << (i + 1) << "=";
         cin >> p[i].x;
         cout << "\n\ty" << (i + 1) << "=";
         cin >> p[i].y;
      }
      p[i].x = p[0].x;
      p[i].y = p[0].y;
      xmin = xmax = p[0].x;
      ymin = ymax = p[0].y;
   }
   else
      cout << "\n Enter valid no. of vertices.";
}
void poly::calcs()
{
   for (int i = 0; i < v; i++)
   {
      if (xmin > p[i].x)
         xmin = p[i].x;
      if (xmax < p[i].x)
         xmax = p[i].x;
      if (ymin > p[i].y)
         ymin = p[i].y;
      if (ymax < p[i].y)
         ymax = p[i].y;
   }
}
void poly::display()
{
   int ch1;
   char ch = 'y';
   float s, s2;
   do
   {
      cout << "\n\nMENU:";
      cout << "\n\n\t1 . Scan line Fill ";
      cout << "\n\n\t2 . Exit ";
      cout << "\n\nEnter your choice:";
      cin >> ch1;
      switch (ch1)
      {
      case 1:
         s = ymin + 0.01;
         delay(100);
         cleardevice();
         while (s <= ymax)
         {
            ints(s);
            sort(s);
            s++;
         }
         break;
      case 2:
         exit(0);
      }
      cout << "Do you want to continue?: ";
      cin >> ch;
   } while (ch == 'y' || ch == 'Y');
}
void poly::ints(float z)
{
   int x1, x2, y1, y2, temp;
   c = 0;
   for (int i = 0; i < v; i++)
   {
      x1 = p[i].x;
      y1 = p[i].y;
      x2 = p[i + 1].x;
      y2 = p[i + 1].y;
      if (y2 < y1)
      {
         temp = x1;
         x1 = x2;
         x2 = temp;
         temp = y1;
         y1 = y2;
         y2 = temp;
      }
      if (z <= y2 && z >= y1)
      {
         if ((y1 - y2) == 0)
            x = x1;
         else
         {
            x = ((x2 - x1) * (z - y1)) / (y2 - y1);
            x = x + x1;
         }
         if (x <= xmax && x >= xmin)
            inter[c++] = x;
      }
   }
}
void poly::sort(int z) // sorting
{
   int temp, j, i;
   for (i = 0; i < v; i++)
   {
      line(p[i].x, p[i].y, p[i + 1].x, p[i + 1].y);
   }
   delay(100);
   for (i = 0; i < c; i += 2)
   {
      delay(100);
      line(inter[i], z, inter[i + 1], z);
   }
}
int main() // main
{
   int cl;
   initwindow(500, 600);
   cleardevice();
   poly x;
   x.read();
   x.calcs();
   cleardevice();
   cout << "\n\tEnter The Color You Want :(In Range 0 To 15 )->"; // selecting color
   cin >> cl;
   setcolor(cl);
   x.display();

   closegraph(); // closing graph
   getch();
   return 0;
}