Sutherland Hodgman polygon clipping

//Sutherland Hodgman polygon clipping

#include<iostream.h>

#include<conio.h>

#include<graphics.h>

#define round(a) ((int)(a+0.5))

int k;

float xmin,ymin,xmax,ymax,arr[20],m;

void clipl(float x1,float y1,float x2,float y2)

{

            if(x2-x1)

                        m=(y2-y1)/(x2-x1);

            else

                        m=100000;

            if(x1 >= xmin && x2 >= xmin)

            {

                        arr[k]=x2;

                        arr[k+1]=y2;

                        k+=2;

            }

            if(x1 < xmin && x2 >= xmin)

            {

                        arr[k]=xmin;

                        arr[k+1]=y1+m*(xmin-x1);

                        arr[k+2]=x2;

                        arr[k+3]=y2;

                        k+=4;

            }

            if(x1 >= xmin  && x2 < xmin)

            {

                        arr[k]=xmin;

                        arr[k+1]=y1+m*(xmin-x1);

                        k+=2;

            }

}

void clipt(float x1,float y1,float x2,float y2)

{

            if(y2-y1)

                        m=(x2-x1)/(y2-y1);

            else

                        m=100000;

            if(y1 <= ymax && y2 <= ymax)

            {

                        arr[k]=x2;

                        arr[k+1]=y2;

                        k+=2;

            }

            if(y1 > ymax && y2 <= ymax)

            {

                        arr[k]=x1+m*(ymax-y1);

                        arr[k+1]=ymax;

                        arr[k+2]=x2;

                        arr[k+3]=y2;

                        k+=4;

            }

            if(y1 <= ymax  && y2 > ymax)

            {

                        arr[k]=x1+m*(ymax-y1);

                        arr[k+1]=ymax;

                        k+=2;

            }

}

void clipr(float x1,float y1,float x2,float y2)

{

            if(x2-x1)

                        m=(y2-y1)/(x2-x1);

            else

                        m=100000;

            if(x1 <= xmax && x2 <= xmax)

            {

                        arr[k]=x2;

                        arr[k+1]=y2;

                        k+=2;

            }

            if(x1 > xmax && x2 <= xmax)

            {

                        arr[k]=xmax;

                        arr[k+1]=y1+m*(xmax-x1);

                        arr[k+2]=x2;

                        arr[k+3]=y2;

                        k+=4;

            }

            if(x1 <= xmax  && x2 > xmax)

            {

                        arr[k]=xmax;

                        arr[k+1]=y1+m*(xmax-x1);

                        k+=2;

            }

}

void clipb(float x1,float y1,float x2,float y2)

{

            if(y2-y1)

                        m=(x2-x1)/(y2-y1);

            else

                        m=100000;

            if(y1 >= ymin && y2 >= ymin)

            {

                        arr[k]=x2;

                        arr[k+1]=y2;

                        k+=2;

            }

            if(y1 < ymin && y2 >= ymin)

            {

                        arr[k]=x1+m*(ymin-y1);

                        arr[k+1]=ymin;

                        arr[k+2]=x2;

                        arr[k+3]=y2;

                        k+=4;

            }

            if(y1 >= ymin  && y2 < ymin)

            {

                        arr[k]=x1+m*(ymin-y1);

                        arr[k+1]=ymin;

                        k+=2;

            }

}

void main()

{

            int gdriver=DETECT,gmode,n,poly[20];

            float xi,yi,xf,yf,polyy[20];

            clrscr();

            cout<<"Coordinates of rectangular clip window :\nxmin,ymin             :";

            cin>>xmin>>ymin;

            cout<<"xmax,ymax             :";

            cin>>xmax>>ymax;

            cout<<"\n\nPolygon to be clipped :\nNumber of sides       :";

            cin>>n;

            cout<<"Enter the coordinates :";

            for(int i=0;i<2*n;i++)

            cin>>polyy[i];

            polyy[i]=polyy[0];

            polyy[i+1]=polyy[1];

            for(i=0;i < 2*n+2;i++)

                        poly[i]=round(polyy[i]);

            initgraph(&gdriver,&gmode,"C:\\TC\\BGI");

            setcolor(RED);

            rectangle(xmin,ymax,xmax,ymin);

            cout<<"\t\tUNCLIPPED POLYGON";

            setcolor(WHITE);

            fillpoly(n,poly);

            getch();

            cleardevice();

            k=0;

            for(i=0;i < 2*n;i+=2)

                        clipl(polyy[i],polyy[i+1],polyy[i+2],polyy[i+3]);

            n=k/2;

            for(i=0;i < k;i++)

                        polyy[i]=arr[i];

            polyy[i]=polyy[0];

            polyy[i+1]=polyy[1];

            k=0;

            for(i=0;i < 2*n;i+=2)

                        clipt(polyy[i],polyy[i+1],polyy[i+2],polyy[i+3]);

            n=k/2;

            for(i=0;i < k;i++)

                        polyy[i]=arr[i];

            polyy[i]=polyy[0];

            polyy[i+1]=polyy[1];

            k=0;

            for(i=0;i < 2*n;i+=2)

                        clipr(polyy[i],polyy[i+1],polyy[i+2],polyy[i+3]);

            n=k/2;

            for(i=0;i < k;i++)

                        polyy[i]=arr[i];

            polyy[i]=polyy[0];

            polyy[i+1]=polyy[1];

            k=0;

            for(i=0;i < 2*n;i+=2)

                        clipb(polyy[i],polyy[i+1],polyy[i+2],polyy[i+3]);

            for(i=0;i < k;i++)

                        poly[i]=round(arr[i]);

            if(k)

                        fillpoly(k/2,poly);

            setcolor(RED);

            rectangle(xmin,ymax,xmax,ymin);

            cout<<"\tCLIPPED POLYGON";

            getch();

            closegraph();

}

Output: