//SUTHERLAND HODGEMAN POLYGON CLIPPING
#include<stdio.h>
#include<graphics.h>
#include<math.h>
typedef struct
{
float x;
float y;
}PT;
int n;
main()
{
int i,j,gd,gm;
PT d,p1,p2,p[20],pi1,pi2,pp[20];
detectgraph(&gd,&gm);
initgraph(&gd,&gm,"");
printf("Enter coordinates (left,top) of point1 : ");
scanf("%f%f",&p1.x,&p1.y);
printf("Enter coordinates (right,bottom) of point2 : ");
scanf("%f%f",&p2.x,&p2.y);
printf("Enter the number of vertex : ");
scanf("%d",&n);
for(i=0;i<n;i++)
{
printf("Enter coordinates of vertex%d : ",i+1);
scanf("%f%f",&p[i].x,&p[i].y);
}
p[i].x = p[0].x;
p[i].y = p[0].y;
cleardevice();
drawpolygon(p,n);
rectangle(p1.x,p1.y,p2.x,p2.y);
getch();
left(p1,p,pp);
right(p2,p,pp);
top(p1,p,pp);
bottom(p2,p,pp);
cleardevice();
rectangle(p1.x,p1.y,p2.x,p2.y);
drawpolygon(p,n);
getch();
closegraph();
}
left(PT p1,PT p[20],PT pp[20])
{
int i,j=0;
for(i=0;i<n;i++)
{
if(p[i].x < p1.x && p[i+1].x >= p1.x)
{
if(p[i+1].x-p[i].x!=0)
{
pp[j].y = (p[i+1].y-p[i].y)/(p[i+1].x-p[i].x)* (p1.x-p[i].x)+p[i].y;
}
else
{
pp[j].y = p[i].y;
}
pp[j].x = p1.x;
j++;
pp[j].x=p[i+1].x;
pp[j].y=p[i+1].y;
j++;
}
if(p[i].x > p1.x && p[i+1].x >= p1.x)
{
pp[j].y = p[i+1].y;
pp[j].x = p[i+1].x;
j++;
}
if(p[i].x > p1.x && p[i+1].x <= p1.x)
{
if(p[i+1].x-p[i].x!=0)
{
pp[j].y = (p[i+1].y-p[i].y)/(p[i+1].x-p[i].x)* (p1.x-p[i].x)+p[i].y;
}
else
{
pp[j].y = p[i].y;
}
pp[j].x = p1.x;
j++;
}
}
for(i=0;i<j;i++)
{
p[i].x = pp[i].x;
p[i].y = pp[i].y;
}
p[i].x = pp[0].x;
p[i].y = pp[0].y;
n=j;
}
right(PT p2,PT p[20],PT pp[20])
{
int i,j=0;
for(i=0;i<n;i++)
{
if(p[i].x > p2.x && p[i+1].x <= p2.x)
{
if(p[i+1].x-p[i].x!=0)
{
pp[j].y = (p[i+1].y-p[i].y)/(p[i+1].x-p[i].x)* (p2.x-p[i].x)+p[i].y;
}
else
{
pp[j].y = p[i].y;
}
pp[j].x = p2.x;
j++;
pp[j].x=p[i+1].x;
pp[j].y=p[i+1].y;
j++;
}
if(p[i].x < p2.x && p[i+1].x <= p2.x)
{
pp[j].y = p[i+1].y;
pp[j].x = p[i+1].x;
j++;
}
if(p[i].x < p2.x && p[i+1].x >= p2.x)
{
if(p[i+1].x-p[i].x!=0)
{
pp[j].y = (p[i+1].y-p[i].y)/(p[i+1].x-p[i].x)* (p2.x-p[i].x)+p[i].y;
}
else
{
pp[j].y = p[i].y;
}
pp[j].x = p2.x;
j++;
}
}
for(i=0;i<j;i++)
{
p[i].x = pp[i].x;
p[i].y = pp[i].y;
}
p[i].x = pp[0].x;
p[i].y = pp[0].y;
n=j;
}
top(PT p1,PT p[20],PT pp[20])
{
int i,j=0;
for(i=0;i<n;i++)
{
if(p[i].y < p1.y && p[i+1].y >= p1.y)
{
if(p[i+1].y-p[i].y!=0)
{
pp[j].x = (p[i+1].x-p[i].x)/(p[i+1].y-p[i].y)* (p1.y-p[i].y)+p[i].x;
}
else
{
pp[j].x = p[i].x;
}
pp[j].y = p1.y;
j++;
pp[j].x=p[i+1].x;
pp[j].y=p[i+1].y;
j++;
}
if(p[i].y > p1.y && p[i+1].y >= p1.y)
{
pp[j].y = p[i+1].y;
pp[j].x = p[i+1].x;
j++;
}
if(p[i].y > p1.y && p[i+1].y <= p1.y)
{
if(p[i+1].y-p[i].y!=0)
{
pp[j].x = (p[i+1].x-p[i].x)/(p[i+1].y-p[i].y)* (p1.y-p[i].y)+p[i].x;
}
else
{
pp[j].x = p[i].x;
}
pp[j].y = p1.y;
j++;
}
}
for(i=0;i<j;i++)
{
p[i].x = pp[i].x;
p[i].y = pp[i].y;
}
p[i].x = pp[0].x;
p[i].y = pp[0].y;
n=j;
}
bottom(PT p2,PT p[20],PT pp[20])
{
int i,j=0;
for(i=0;i<n;i++)
{
if(p[i].y > p2.y && p[i+1].y <= p2.y)
{
if(p[i+1].y-p[i].y!=0)
{
pp[j].x = (p[i+1].x-p[i].x)/(p[i+1].y-p[i].y)* (p2.y-p[i].y)+p[i].x;
}
else
{
pp[j].x = p[i].x;
}
pp[j].y = p2.y;
j++;
pp[j].x=p[i+1].x;
pp[j].y=p[i+1].y;
j++;
}
if(p[i].y < p2.y && p[i+1].y <= p2.y)
{
pp[j].y = p[i+1].y;
pp[j].x = p[i+1].x;
j++;
}
if(p[i].y < p2.y && p[i+1].y >= p2.y)
{
if(p[i+1].y-p[i].y!=0)
{
pp[j].x = (p[i+1].x-p[i].x)/(p[i+1].y-p[i].y)* (p2.y-p[i].y)+p[i].x;
}
else
{
pp[j].x = p[i].x;
}
pp[j].y = p2.y;
j++;
}
}
for(i=0;i<j;i++)
{
p[i].x = pp[i].x;
p[i].y = pp[i].y;
}
p[i].x = pp[0].x;
p[i].y = pp[0].y;
n=j;
}
drawpolygon(PT x[20],int n)
{
int i;
for(i=0;i<n-1;i++)
{
line(x[i].x,x[i].y,x[i+1].x,x[i+1].y);
}
line(x[i].x,x[i].y,x[0].x,x[0].y);
}
SAMPLE OUTPUT:
