C Program to implement the Cohen-Sutherland line-clipping algorithm.

#include <stdio.h>
#include <stdlib.h>
#include <graphics.h>
#define MAX 20
 
enum { TOP = 0x1, BOTTOM = 0x2, RIGHT = 0x4, LEFT = 0x8 };
 
enum { FALSE, TRUE };
typedef unsigned int outcode;
 
outcode compute_outcode(int x, int y,
int xmin, int ymin, int xmax, int ymax)
{
outcode oc = 0;
 
if (y > ymax)
oc |= TOP;
else if (y < ymin)
oc |= BOTTOM;
 
 
if (x > xmax)
oc |= RIGHT;
else if (x < xmin)
oc |= LEFT;
 
return oc;
}
 
void cohen_sutherland (double x1, double y1, double x2, double y2,
double xmin, double ymin, double xmax, double ymax)
{
int accept;
int done;
outcode outcode1, outcode2;
 
accept = FALSE;
done = FALSE;
 
outcode1 = compute_outcode (x1, y1, xmin, ymin, xmax, ymax);
outcode2 = compute_outcode (x2, y2, xmin, ymin, xmax, ymax);
do
{
if (outcode1 == 0 && outcode2 == 0)
{
accept = TRUE;
done = TRUE;
}
else if (outcode1 & outcode2)
{
done = TRUE;
}
else
{
double x, y;
int outcode_ex = outcode1 ? outcode1 : outcode2;
if (outcode_ex & TOP)
{
x = x1 + (x2 - x1) * (ymax - y1) / (y2 - y1);
y = ymax;
}
 
else if (outcode_ex & BOTTOM)
{
x = x1 + (x2 - x1) * (ymin - y1) / (y2 - y1);
y = ymin;
}
else if (outcode_ex & RIGHT)
{
y = y1 + (y2 - y1) * (xmax - x1) / (x2 - x1);
x = xmax;
}
else
{
y = y1 + (y2 - y1) * (xmin - x1) / (x2 - x1);
x = xmin;
}
if (outcode_ex == outcode1)
{
x1 = x;
y1 = y;
outcode1 = compute_outcode (x1, y1, xmin, ymin, xmax, ymax);
}
else
{
x2 = x;
y2 = y;
outcode2 = compute_outcode (x2, y2, xmin, ymin, xmax, ymax);
}
}
} while (done == FALSE);
 
if (accept == TRUE)
line (x1, y1, x2, y2);
}
 
 
 
void main()
{
int n;
int i, j;
int ln[MAX][4];
int clip[4];
int gd = DETECT, gm;
 
printf ("Enter the number of lines to be clipped");
scanf ("%d", &n);
 
printf ("Enter the x- and y-coordinates of the line-endpoints:\n");
for (i=0; i<n; i++)
for (j=0; j<4; j++)
scanf ("%d", &ln[i][j]);
 
printf ("Enter the x- and y-coordinates of the left-top and right-");
printf ("bottom corners\nof the clip window:\n");
for (i=0; i<4; i++)
scanf ("%d", &clip[i]);
 
initgraph (&gd, &gm, "..//bgi");
 
rectangle (clip[0], clip[1], clip[2], clip[3]);
for (i=0; i<n; i++)
line (ln[i][0], ln[i][1], ln[i][2], ln[i][3]);
getch();
cleardevice();
rectangle (clip[0], clip[1], clip[2], clip[3]);
for (i=0; i<n; i++)
{
cohen_sutherland (ln[i][0], ln[i][1], ln[i][2], ln[i][3],
clip[0], clip[1], clip[2], clip[3]);
getch();
}
closegraph();
}