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# Program of Sutherland Hodgemann Algorithm for Polygon clipping

Posted By: Easy Tutor     Category: C++ Programming     Views: 20955

## Code for Program of Sutherland Hodgemann Algorithm for Polygon clipping in C++ Programming

```#include<stdio.h>
#include<conio.h>
#include<iostream.h>
#include<graphics.h>
#define ROUND(a) ((int)(a+0.5))
#define n 4

#define LEFT_EDGE 0x1
#define RIGHT_EDGE 0x2
#define BOTTOM_EDGE 0x4
#define TOP_EDGE 0x8

#define INSIDE(a)  (!a)
#define REJECT(a,b) (a&b)
#define ACCEPT(a,b) (!(a|b))

typedef struct wcpt2
{
int x,y;
}wcpt2;

typedef struct dcpt
{
int x,y;
}dcpt;

void main()
{
int gd=DETECT,gm;
int left,top,right,bottom;
int x1,x2,y1,y2;
int maxx, maxy;
/* our polygon array */int poly[10];
void clipline(dcpt,dcpt,wcpt2,wcpt2);
clrscr();

initgraph(&gd,&gm,"c:\\tc30\\bgi");
maxx = getmaxx()/4;
maxy = getmaxy()/4;

poly[0] = 20;        /* 1st vertex */
poly[1] = maxy / 2;

poly[2] = maxx - 10; /* 2nd */
poly[3] = 10;

poly[4] = maxx - 50; /* 3rd */
poly[5] = maxy - 20;

poly[6] = maxx / 2;  /* 4th */
poly[7] = maxy / 2;

/*   drawpoly doesn't automatically close   the polygon, so we close it.*/
poly[8] = poly[0];
poly[9] = poly[1];

/* draw the polygon */
drawpoly(5, poly);

rectangle(20,25,80,125);
wcpt2 pt1,pt2;
dcpt winmin,winmax;

winmin.x=20;
winmin.y=25;
winmax.x=80;
winmax.y=125;

pt1.x=20;
pt1.y=maxy/2;
pt2.x=maxx-10;
pt2.y=10;

//    clipline(winmin,winmax,pt1,pt2);int i=0;
for(int index=0;index<n;index++)
{
if(index==n-1)
{
pt1.x=poly[i];
pt1.y=poly[i+1];
i=0;
pt2.x=poly[i];
pt2.y=poly[i+1];
clipline(winmin,winmax,pt1,pt2);
}
else
{
pt1.x=poly[i];
pt1.y=poly[i+1];
pt2.x=poly[i+2];
pt2.y=poly[i+3];
clipline(winmin,winmax,pt1,pt2);
}
i+=2;
}
pt1.x=poly[i];
pt1.y=poly[i+1];
clipline(winmin,winmax,pt1,pt2);
getch();
}

unsigned char encode(wcpt2 pt,dcpt winmin,dcpt winmax)
{
unsigned char code=0x00;
if(pt.x < winmin.x)
code=code | LEFT_EDGE;
if(pt.x > winmax.x)
code=code | RIGHT_EDGE;
if(pt.y < winmin.y)
code=code | TOP_EDGE;
if(pt.y > winmax.y)
code=code | BOTTOM_EDGE;
return code;
}

void swappts(wcpt2 *p1,wcpt2 *p2)
{
wcpt2 tmp;
tmp = *p1;
*p1 = *p2;
*p2 = tmp;
}

void swapcode(unsigned char *c1,unsigned char *c2)
{
unsigned char tmp;
tmp = *c1;
*c1 = *c2;
*c2 = tmp;
}

void clipline(dcpt winmin,dcpt winmax,wcpt2 p1,wcpt2 p2)
{
unsigned char encode(wcpt2,dcpt,dcpt);
unsigned char code1,code2;
int done = 0 , draw = 0;
float m;
void swapcode(unsigned char *c1,unsigned char *c2);
void swappts(wcpt2 *p1,wcpt2 *p2);

while(!done)
{
code1 = encode(p1,winmin,winmax);
code2 = encode(p2,winmin,winmax);
if(ACCEPT(code1,code2))
{
draw = 1;
done = 1;
}
elseif(REJECT(code1,code2))
done = 1;
elseif(INSIDE(code1))
{
swappts(&p1,&p2);
swapcode(&code1,&code2);
}
if(code1 & LEFT_EDGE)
{
p1.y += (winmin.x - p1.x) *  (p2.y - p1.y) / (p2.x - p1.x);
p1.x = winmin.x;
}
elseif(code1 & RIGHT_EDGE)
{
p1.y += (winmax.x - p1.x) *  (p2.y - p1.y) / (p2.x - p1.x);
p1.x = winmax.x;
}
elseif(code1 & TOP_EDGE)
{
if(p2.x != p1.x)
p1.x += (winmin.y - p1.y) *  (p2.x - p1.x) / (p2.y - p1.y);
p1.y = winmin.y;
}
elseif(code1 & BOTTOM_EDGE)
{
if(p2.x != p1.x)
p1.x += (winmax.y - p1.y) *  (p2.x - p1.x) / (p2.y - p1.y);
p1.y = winmax.y;
}
}
if(draw)
{
setcolor(5);
line(p1.x,p1.y,p2.x,p2.y);
}
}
```
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