The document describes an experiment on line clipping using the Cohen-Sutherland algorithm. It includes: 1) The aim is to display the 4-bit region codes of line endpoints and clip lines intersecting the screen window using Cohen-Sutherland clipping. 2) The tasks involve displaying region codes, and clipping lines intersecting at one point or multiple points. 3) Pseudocode is provided for the algorithms to display region codes, clip lines intersecting at one point, and lines at multiple points.

1. Experiment no. – 3.1
Student Name: Krishna Kumar UID: 19BCS2605
Branch: CSE - 11 Section/Group : ‘C’
Semester: 5th
Date of Performance: 21 Oct 2021
Subject Name: Computer Graphics Lab Subject Code: CSP - 305
1. Aim/Overview of the practical: a) To display 4-bit region code for end points of a line and
check whether line is completely on the screen or off the screen
b) To clip a line intersecting at one point with given window using Cohen
Sutherland Line Clipping algorithm.
c) To clip a line intersecting at Two or more points with given window using
Cohen Sutherland Line Clipping algorithm
2. Task to be done: a) To display 4-bit region code for end points of a line
b) To clip a line intersecting at one point with given window
c) To clip a line intersecting at Two or more points with given window
3. Algorithm :
a) algorithms for display 4-bit region code for end points of a line
Step 1: Start
Step 1.1: taking two point, starting point and end point of line for user
Step 1.2: taking two co-ordinate of rectangle, starting co-ordinate and end co-
ordinate of rectangle for user
Step 1. 4: Assign a region code for two endpoints of given line
Step 2 : If both endpoints have a region code 0000 then given line is completely
inside and we will keep this line

2. Step 3 : If step 2 fails, perform the logical AND operation for both region codes.
Step 3.1 : If the result is not 0000, then given line is completely outside.
Step 3.2 : Else line is partially inside.
Step 3.2.a : Choose an endpoint of the line that is outside the given rectangle.
Step 3.2.b : Find the intersection point of the rectangular boundary (based on
region code).
Step 3.2.c : Replace endpoint with the intersection point and update the region
code.
Step 3.2.d : Repeat step 2 until we find a clipped line either trivially accepted or
rejected.
Step 4 : Repeat step 1 for all lines
Step 5: using while for taking point of line again and again form user.
Step 6: Displaying window, line and line in side window at a green colour at
green colour
Step 7: End
b) algorithms for clip a line intersecting at one point with given window
Step 1: Start
Step 1.1: taking two point, starting point and end point of line for user
Step 1.2: taking two co-ordinate of rectangle, starting co-ordinate and end co-
ordinate of rectangle for user
Step 1.3 : Assign a region code for two endpoints of given line
Step 2 : If both endpoints have a region code 0000 then given line is completely
inside and we will keep this line
Step 3 : If step 2 fails, perform the logical AND operation for both region codes.
Step 3.1 : If the result is not 0000, then given line is completely outside.
Step 3.2 : Else line is partially inside.
Step 3.2.a : Choose an endpoint of the line that is outside the given rectangle.
Step 3.2.b : Find the intersection point of the rectangular boundary (based on
region code).
Step 3.2.c : Replace endpoint with the intersection point and update the region
code.
Step 3.2.d : Repeat step 2 until we find a clipped line either trivially accepted or
rejected.

3. Step 4 : Repeat step 1 for all lines
Step 5: Displaying window and line before line clipping and after line clipping
at green colour
Step 6: End
c) algorithms for clip a line intersecting at Two or more points with given window
Step 1: Start
Step 1.1: taking two point, starting point and end point of line for user
Step 1.2: taking two co-ordinate of rectangle, starting co-ordinate and end co-
ordinate of rectangle for user
Step 1.3 : Assign a region code for two endpoints of given line
Step 2 : If both endpoints have a region code 0000 then given line is completely
inside and we will keep this line
Step 3 : If step 2 fails, perform the logical AND operation for both region codes.
Step 3.1 : If the result is not 0000, then given line is completely outside.
Step 3.2 : Else line is partially inside.
Step 3.2.a : Choose an endpoint of the line that is outside the given rectangle.
Step 3.2.b : Find the intersection point of the rectangular boundary (based on
region code).
Step 3.2.c : Replace endpoint with the intersection point and update the region
code.
Step 3.2.d : Repeat step 2 until we find a clipped line either trivially accepted or
rejected.
Step 4 : Repeat step 1 for all lines
Step 5: Displaying window and line before line clipping and after line clipping
Step 6: End
4. Programming Code:
a) Code for display 4-bit region code for end points of a line
#include<iostream>
#include<graphics.h>
#include<math.h>

4. #include<conio.h>
using namespace std;
class CohenSutherLandAlgo
{
private:
double x1,y1,x2,y2;
double x_max,y_max,x_min,y_min;
const int INSIDE = 0;
const int LEFT = 1;
const int RIGHT = 2;
const int BOTTOM = 4;
const int TOP = 8;
public:
CohenSutherLandAlgo()
{
x1 = 0.0;
x2 = 0.0;
y1 = 0.0;
y2 = 0.0;
}
void getCoordinates();
void getClippingRectangle();
int generateCode(double x, double y);
void cohenSutherland();
};
void CohenSutherLandAlgo::getCoordinates()
{
std::cout << "Enter Co-ordinates of P1(X1,Y1) of Line Segment : ";
std::cin >> x1>>y1;
std::cout << "Enter Co-ordinates of P2(X2,Y2) of Line Segment :";
std::cin >> x2>>y2;
std::cout<<endl;
setcolor(WHITE);
line(x1,y1,x2,y2);
}
void CohenSutherLandAlgo::getClippingRectangle()
{
std::cout << "Enter the Co-ordinates of Interested Rectangle."<<endl;
std::cout << "Enter the X_MAX and Enter the Y_MAX : ";
std::cin >> x_max>>y_max;
std::cout << "Enter the X_MIN and Enter the Y_MIN : ";

5. std::cin >> x_min>>y_min;
rectangle(x_min,y_min,x_max,y_max);
}
int CohenSutherLandAlgo::generateCode(double x, double y)
{
int code = INSIDE;
if (x < x_min)
code |= LEFT;
else if (x > x_max)
code |= RIGHT;
if (y < y_min)
code |= BOTTOM;
else if (y > y_max)
code |= TOP;
return code;
}
void CohenSutherLandAlgo::cohenSutherland()
{
int code1 = generateCode(x1, y1);
int code2 = generateCode(x2, y2);
bool accept = false;
while (true)
{
if ((code1 == 0) && (code2 == 0))
{
accept = true;
break;
}
else if (code1 & code2)
{
break;
}
else
{
int code_out;
double x, y;
if (code1 != 0)
code_out = code1;
else
code_out = code2;
if (code_out & TOP)

6. {
x = x1 + (x2 - x1) * (y_max - y1) / (y2 - y1);
y = y_max;
}
else if (code_out & BOTTOM)
{
x = x1 + (x2 - x1) * (y_min - y1) / (y2 - y1);
y = y_min;
}
else if (code_out & RIGHT)
{
y = y1 + (y2 - y1) * (x_max - x1) / (x2 - x1);
x = x_max;
}
else if (code_out & LEFT)
{
y = y1 + (y2 - y1) * (x_min - x1) / (x2 - x1);
x = x_min;
}
if (code_out == code1)
{
x1 = x;
y1 = y;
code1 = generateCode(x1, y1);
}
else
{
x2 = x;
y2 = y;
code2 = generateCode(x2, y2);
}
}
}
if (accept)
{ std::cout<<endl;
std::cout <<"Line accepted from " <<"("<< x1 << ", "
<< y1 << ")" << " to "<< "(" << x2 << ", " << y2 << ")" <<
std::endl;
setcolor(GREEN);
line(x1,y1,x2,y2);
}

7. else
std::cout << "Line rejected" << std::endl;
}
int main()
{
int gd=DETECT,gm;
initgraph(&gd,&gm,"c:turboc3bgi");
int x;
outtextxy(5,5,"White color that part of line segment is not accept ");
setcolor(GREEN);
outtextxy(5,20,"Green color that part of line segment is accept ");
setcolor(WHITE);
CohenSutherLandAlgo c;
c.getClippingRectangle();
do{
c.getCoordinates();
c.cohenSutherland();
std::cout<<endl;
cout<<"Please press 1 (one) for continue :";
cin>>x;
}
while(x==1);
getch();
closegraph();
}
b) Code for clip a line intersecting at one point with given window
#include<iostream>
#include<graphics.h>
#include<math.h>
#include<conio.h>
using namespace std;
class CohenSutherLandAlgo
{
private:

8. double x1,y1,x2,y2;
double x_max,y_max,x_min,y_min;
const int INSIDE = 0;
const int LEFT = 1;
const int RIGHT = 2;
const int BOTTOM = 4;
const int TOP = 8;
public:
CohenSutherLandAlgo()
{
x1 = 0.0;
x2 = 0.0;
y1 = 0.0;
y2 = 0.0;
}
void getCoordinates();
void getClippingRectangle();
int generateCode(double x, double y);
void cohenSutherland();
};
void CohenSutherLandAlgo::getCoordinates()
{
std::cout << "Enter Co-ordinates of P1(X1,Y1) of Line Segment : ";
std::cin >> x1>>y1;
std::cout << "Enter Co-ordinates of P2(X2,Y2) of Line Segment :";
std::cin >> x2>>y2;
std::cout<<endl;
line(x1,y1,x2,y2);
}
void CohenSutherLandAlgo::getClippingRectangle()
{
std::cout << "Enter the Co-ordinates of Interested Rectangle."<<endl;
std::cout << "Enter the X_MAX and Enter the Y_MAX : ";

9. std::cin >> x_max>>y_max;
std::cout << "Enter the X_MIN and Enter the Y_MIN : ";
std::cin >> x_min>>y_min;
rectangle(x_min,y_min,x_max,y_max);
outtextxy(x_min,y1-20,"Before line Clipping");
setcolor(GREEN);
outtextxy(x_max+50,y1-20,"After line Clipping");
rectangle(x_max+50,y_min,x_max+50+x_max-x_min,y_max);
}
int CohenSutherLandAlgo::generateCode(double x, double y)
{
int code = INSIDE;
if (x < x_min)
code |= LEFT;
else if (x > x_max)
code |= RIGHT;
if (y < y_min)
code |= BOTTOM;
else if (y > y_max)
code |= TOP;
return code;
}
void CohenSutherLandAlgo::cohenSutherland()
{
int code1 = generateCode(x1, y1);
int code2 = generateCode(x2, y2);
bool accept = false;
while (true)
{
if ((code1 == 0) && (code2 == 0))
{
accept = true;
break;
}
else if (code1 & code2)
{

10. break;
}
else
{
int code_out;
double x, y;
if (code1 != 0)
code_out = code1;
else
code_out = code2;
if (code_out & TOP)
{
x = x1 + (x2 - x1) * (y_max - y1) / (y2 - y1);
y = y_max;
}
else if (code_out & BOTTOM)
{
x = x1 + (x2 - x1) * (y_min - y1) / (y2 - y1);
y = y_min;
}
else if (code_out & RIGHT)
{
y = y1 + (y2 - y1) * (x_max - x1) / (x2 - x1);
x = x_max;
}
else if (code_out & LEFT)
{
y = y1 + (y2 - y1) * (x_min - x1) / (x2 - x1);
x = x_min;
}
if (code_out == code1)
{
x1 = x;
y1 = y;
code1 = generateCode(x1, y1);
}

11. else
{
x2 = x;
y2 = y;
code2 = generateCode(x2, y2);
}
}
}
if (accept)
{ std::cout<<endl;
std::cout <<"Line accepted from " <<"("<< x1 << ", "
<< y1 << ")" << " to "<< "(" << x2 << ", " << y2 << ")" <<
std::endl;
setcolor(GREEN);
line(x1+x_max-x_min+50,y1,x2+x_max-x_min+50,y2);
}
else
std::cout << "Line rejected" << std::endl;
}
int main()
{
int gd=DETECT,gm;
initgraph(&gd,&gm,"c:turboc3bgi");
CohenSutherLandAlgo c;
c.getCoordinates();
c.getClippingRectangle();
c.cohenSutherland();
getch();
closegraph();
}
c) Code for clip a line intersecting at Two or more points with given window
#include<iostream>
#include<graphics.h>

12. #include<math.h>
#include<conio.h>
using namespace std;
class CohenSutherLandAlgo
{
private:
double x1,y1,x2,y2;
double x_max,y_max,x_min,y_min;
const int INSIDE = 0;
const int LEFT = 1;
const int RIGHT = 2;
const int BOTTOM = 4;
const int TOP = 8;
public:
CohenSutherLandAlgo()
{
x1 = 0.0;
x2 = 0.0;
y1 = 0.0;
y2 = 0.0;
}
void getCoordinates();
void getClippingRectangle();
int generateCode(double x, double y);
void cohenSutherland();
};
void CohenSutherLandAlgo::getCoordinates()
{
std::cout << "Enter Co-ordinates of P1(X1,Y1) of Line Segment : ";
std::cin >> x1>>y1;
std::cout << "Enter Co-ordinates of P2(X2,Y2) of Line Segment :";
std::cin >> x2>>y2;
std::cout<<endl;
line(x1,y1,x2,y2);

13. }
void CohenSutherLandAlgo::getClippingRectangle()
{
std::cout << "Enter the Co-ordinates of Interested Rectangle."<<endl;
std::cout << "Enter the X_MAX and Enter the Y_MAX : ";
std::cin >> x_max>>y_max;
std::cout << "Enter the X_MIN and Enter the Y_MIN : ";
std::cin >> x_min>>y_min;
rectangle(x_min,y_min,x_max,y_max);
outtextxy(x_min,y1-20,"Before line Clipping");
setcolor(GREEN);
outtextxy(x_max+50,y1-20,"After line Clipping");
rectangle(x_max+50,y_min,x_max+50+x_max-x_min,y_max);
}
int CohenSutherLandAlgo::generateCode(double x, double y)
{
int code = INSIDE;
if (x < x_min)
code |= LEFT;
else if (x > x_max)
code |= RIGHT;
if (y < y_min)
code |= BOTTOM;
else if (y > y_max)
code |= TOP;
return code;
}
void CohenSutherLandAlgo::cohenSutherland()
{
int code1 = generateCode(x1, y1);
int code2 = generateCode(x2, y2);
bool accept = false;
while (true)

14. {
if ((code1 == 0) && (code2 == 0))
{
accept = true;
break;
}
else if (code1 & code2)
{
break;
}
else
{
int code_out;
double x, y;
if (code1 != 0)
code_out = code1;
else
code_out = code2;
if (code_out & TOP)
{
x = x1 + (x2 - x1) * (y_max - y1) / (y2 - y1);
y = y_max;
}
else if (code_out & BOTTOM)
{
x = x1 + (x2 - x1) * (y_min - y1) / (y2 - y1);
y = y_min;
}
else if (code_out & RIGHT)
{
y = y1 + (y2 - y1) * (x_max - x1) / (x2 - x1);
x = x_max;
}
else if (code_out & LEFT)
{
y = y1 + (y2 - y1) * (x_min - x1) / (x2 - x1);

15. x = x_min;
}
if (code_out == code1)
{
x1 = x;
y1 = y;
code1 = generateCode(x1, y1);
}
else
{
x2 = x;
y2 = y;
code2 = generateCode(x2, y2);
}
}
}
if (accept)
{ std::cout<<endl;
std::cout <<"Line accepted from " <<"("<< x1 << ", "
<< y1 << ")" << " to "<< "(" << x2 << ", " << y2 << ")" <<
std::endl;
setcolor(GREEN);
line(x1+x_max-x_min+50,y1,x2+x_max-x_min+50,y2);
}
else
std::cout << "Line rejected" << std::endl;
}
int main()
{
int gd=DETECT,gm;
initgraph(&gd,&gm,"c:turboc3bgi");
CohenSutherLandAlgo c;
c.getCoordinates();
c.getClippingRectangle();
c.cohenSutherland();

16. getch();
closegraph();
}
5. Output:
a) Output for display 4-bit region code for end points of a line

17. b) Output for clip a line intersecting at one point with given window
c) Output for clip a line intersecting at Two or more points with given window

18. 6. Learning outcomes (What I have learnt):
1. I have gathered detail knowledge about how to display 4-bit region code for end
points of a line and check whether line is completely on the screen or off the screen
2. I have gathered detail knowledge about how to clip a line intersecting at one point
with given window using Cohen Sutherland Line Clipping algorithm.
3. I have gathered detail knowledge about how to clip a line intersecting at Two or
more points with given window using Cohen Sutherland Line Clipping algorithm
4. I have learn how to display 4-bit region code for end points of a line and check
whether line is completely on the screen or off the screen
5. I have learn how to clip a line intersecting at one point and two or more point with
given window using Cohen Sutherland Line Clipping algorithm.
6. I get to know about proper logic & algorithm in computation of clip a line
intersecting at one point andTwo or more points with given window using Cohen
Sutherland Line Clipping algorithm
7. Evaluation Grid (To be created as per the SOP and Assessment guidelines by the faculty):
Sr. No. Parameters Marks Obtained Maximum Marks
1.
2.
3.