CG 1

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

The Code for above problem is as follows : 

 // Program to Fill a Polygon Using Scan Line Fill Algorithm in C++.  
   
 #include <conio.h>  
 #include <iostream.h>  
 #include <graphics.h>  
 #include <stdlib.h>  
 #include<dos.h>  
   
 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\t SCAN_FILL ALGORITHM";  
   cout<<"\n Enter the no of vertices of polygon:";  
   cin>>v;  
   if(v>2)  
   {  
      for(i=0;i<v; i++)   
      {  
        cout<<"\nEnter the 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 i;  
     float s,s2;  
       s=ymin+0.01;  
      delay(100);  
    for(i=0;i<v;i++)  
      {  
   
        line(p[i].x,p[i].y,p[i+1].x,p[i+1].y); // used draw a polygon  
      }  
      while(s<=ymax)  
      {  
        ints(s);  
        sort(s);  
        s++;  
      }  
      getch();  
   }  
   
 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)   
 {  
   int temp,j,i;  
   
   
      delay(100);  
      for(i=0; i<c;i+=2)  
      {  
        delay(100);  
        line(inter[i],z,inter[i+1],z); // Used to fill the polygon ....  
      }  
 }  
   
 int main()   
 {  
   int gd=DETECT,gm;  
   initgraph(&gd,&gm,"c:\\turboc3\\bgi");  
   
   cleardevice();  
 int cl;  
  poly x;  
   
   
   x.read();  
   x.calcs();  
   cleardevice();  
   cout<<"\n\tEnter the colour u want:(0-15)->"; //Selecting colour  
   cin>>cl;  
   cleardevice();  
   setcolor(cl);  
   x.display();  
   closegraph();   
   getch();  
   return 0;  
 }