A C++ program for Sutherman Hodgeman polygon Clipping algorithm.


#include <stdio.h>
#include <graphics.h>
#include <conio.h>
#include <math.h>
#include <process.h>
#define TRUE 1
#define FALSE 0
typedef unsigned int outcode;
outcode CompOutCode(float x,float y);
enum { TOP = 0x1,
BOTTOM = 0x2,
RIGHT = 0x4,
LEFT = 0x8};
float xmin,xmax,ymin,ymax;
void clip(float x0,float y0,float x1,float y1){
outcode outcode0,outcode1,outcodeOut;
int accept = FALSE,done = FALSE;
outcode0 = CompOutCode(x0,y0);
outcode1 = CompOutCode(x1,y1);
do{
if(!(outcode0|outcode1)){
accept = TRUE;
done = TRUE;}
else
if(outcode0 & outcode1)
done = TRUE;
else{
float x,y;
outcodeOut = outcode0?outcode0:outcode1;
if(outcodeOut & TOP){
x = x0+(x1-x0)*(ymax-y0)/(y1-y0);
y = ymax;}
else
if(outcodeOut & BOTTOM){
x = x0+(x1-x0)*(ymin-y0)/(y1-y0);
y = ymin;}
else
if(outcodeOut & RIGHT){
y = y0+(y1-y0)*(xmax-x0)/(x1-x0);
x = xmax;}
else{
y = y0+(y1-y0)*(xmin-x0)/(x1-x0);
x = xmin;}
if(outcodeOut==outcode0){
x0 = x;
y0 = y;
outcode0 = CompOutCode(x0,y0);}
else{
x1 = x;
y1 = y;
outcode1 = CompOutCode(x1,y1);}}
}while(done==FALSE);
if(accept)
line(x0,y0,x1,y1);
outtextxy(150,20,”POLYGON AFTER CLIPPING”);
rectangle(xmin,ymin,xmax,ymax);}
outcode CompOutCode(float x,float y){
outcode code = 0;
if(y>ymax)
code|=TOP;
else
if(y<ymin)
code|=BOTTOM;
if(x>xmax)
code|=RIGHT;
else
if(x<xmin)
code|=LEFT;
return code;}
int main( ){
float x1,y1,x2,y2;
/* request auto detection */
int gdriver = DETECT, gmode, n,poly[14],i;
printf(“Enter the no of sides of polygon:”);
scanf(“%d”,&n);
printf(“\nEnter the coordinates of polygon\n”);
for(i=0;i<2*n;i++)
{
scanf(“%d”,&poly[i]);
}
poly[2*n]=poly[0];
poly[2*n+1]=poly[1];
printf(“Enter the rectangular coordinates of clipping window\n”);
scanf(“%f%f%f%f”,&xmin,&ymin,&xmax,&ymax);
/* initialize graphics and local variables */
initgraph(&gdriver, &gmode, “c:\\tc\\bgi”);
outtextxy(150,20,”POLYGON BEFORE CLIPPING”);
drawpoly(n+1,poly);
rectangle(xmin,ymin,xmax,ymax);
getch( );
cleardevice( );
for(i=0;i<n;i++)
clip(poly[2*i],poly[(2*i)+1],poly[(2*i)+2],poly[(2*i)+3]);
getch( );
restorecrtmode( );
return 0;
}