# C++ Program to Implement Cohen Sutherland Algorithm

Here is the implementation of Cohen Sutherland Algorithm in C++.

#include<iostream.h>
#include<conio.h>
#include<stdlib.h>
#include<dos.h>
#include<math.h>
#include<graphics.h>

typedef struct coordinate {
int x, y;
char code[4];
}
PT;
void drawwindow();
void drawline(PT p1, PT p2, int cl);
PT setcode(PT p);
int visibility(PT p1, PT p2);
PT resetendpt(PT p1, PT p2);
main() {
int gd = DETECT, gm, v;
PT p1, p2, ptemp;
initgraph( & gd, & gm, "c:\\tc\\bgi ");
cleardevice();
cout << "\n\n\t\tENTER END-POINT 1 (x,y): ";
cin >> p1.x >> p1.y;
cout << "\n\n\t\tENTER END-POINT 2 (x,y): ";
cin >> p2.x >> p2.y;
cleardevice();
drawwindow();
getch();
drawline(p1, p2, 15);
getch();
p1 = setcode(p1);
p2 = setcode(p2);
v = visibility(p1, p2);
switch (v) {
case 0:
cleardevice();
drawwindow();
drawline(p1, p2, 15);
break;
case 1:
cleardevice();
drawwindow();
break;
case 2:
cleardevice();
p1 = resetendpt(p1, p2);
p2 = resetendpt(p2, p1);
drawwindow();
drawline(p1, p2, 15);
break;
}
getch();
closegraph();
return (0);
}
void drawwindow() {
setcolor(RED);
line(150, 100, 450, 100);
line(450, 100, 450, 350);
line(450, 350, 150, 350);
line(150, 350, 150, 100);
}
void drawline(PT p1, PT p2, int cl) {
setcolor(cl);
line(p1.x, p1.y, p2.x, p2.y);
PT setcode(PT p) {
PT ptemp;
if (p.y < 100)
ptemp.code[0] = '1';
else
ptemp.code[0] = '0';
if (p.y > 350)
ptemp.code[1] = '1';
else
ptemp.code[1] = '0';
if (p.x > 450)
ptemp.code[2] = '1';
else
ptemp.code[2] = '0';
if (p.x < 150)
ptemp.code[3] = '1';
else
ptemp.code[3] = '0';
ptemp.x = p.x;
ptemp.y = p.y;
return (ptemp);
}
int visibility(PT p1, PT p2) {
int i, flag = 0;
for (i = 0; i < 4; i++) {
if ((p1.code[i] != '0') || (p2.code[i] != '0'))
flag = 1;
}
if (flag == 0)
return (0);
for (i = 0; i < 4; i++) {
if ((p1.code[i] == p2.code[i]) && (p1.code[i] == '1'))
flag = 0;
}
if (flag == 0)
return (1);
return (2);
}
PT resetendpt(PT p1, PT p2) {
PT temp;
int x, y, i;
float m, k;
if (p1.code[3] == '1')
x = 150;
if (p1.code[2] == '1')
x = 450;
if ((p1.code[3] == '1') || (p1.code[2] == '1')) {
m = (float)(p2.y - p1.y) / (p2.x - p1.x);
k = (p1.y + (m * (x - p1.x)));
temp.y = k;
temp.x = x;
for (i = 0; i < 4; i++)
temp.code[i] = p1.code[i];
if (temp.y <= 350 && temp.y >= 100)
return (temp);
}
if (p1.code[0] == '1')
y = 100;
if (p1.code[1] == '1')
y = 350;
if ((p1.code[0] == '1') || (p1.code[1] == '1')) {
m = (float)(p2.y - p1.y) / (p2.x - p1.x);
k = (float) p1.x + (float)(y - p1.y) / m;
temp.x = k;
temp.y = y;
for (i = 0; i < 4; i++)
temp.code[i] = p1.code[i];
return (temp);
} else
return (p1);
}

Output:

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