CPP code for Shutherland-hodgeman polygon clipping in Computer Graphics

#include<graphics.h>

#include<conio.h>

#include<iostream.h>

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

int k;

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

void clipleft(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 cliptop(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 clipright(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 clipbottom(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 gd=DETECT,gm,n,poly[20];

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

clrscr();

cout<<"coordinates of rectanglular clip window :\nxmin,ymin:";

cin>>xmin>>ymin;

cout<<"xmax,ymax:";

cin>>xmax>>ymax;

cout<<"\n\n polygon to be clipped:\nnumber of sildes:";

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(&gd,&gm,"");

setcolor(RED);

rectangle(xmin,ymax,ymax,ymin);

cout<<"\t\t unclipped polygon";

setcolor(WHITE);

fillpoly(n,poly);

getch();

cleardevice();

k=0;

for(i=0;i<2*n;i+=2)

clipleft(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)

cliptop(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)

clipright(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)

clipbottom(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<<"\t clipped polygon";

getch();

closegraph();

}