COHEN SUTHERLAND 2D LINE CLIPPING

COHEN SUTHERLAND 2D LINE CLIPPING

Aim :

To write a C program to clip a line using Cohen-Sutherland clipping algorithm.

Algorithm:

Step 1: Start the program.

Step 2: Enter the line end points and the window coordinates.

Step 3: Every line end point is assigned a code that identified the location of the point

relative to the boundaries of the clipping rectangle.

Step 4: Check whether the line lies inside the window then it is entirely drawn.

Step 5: Check whether the line lies outside the window then it is entirely clipped.

Step 6: Otherwise check whether the line intersects the window:

a) Calculate differences between end points and clip boundaries.

b) Determine the intersection point and how much of the line is to be discarded.

Step 7: Display the Output.

Step 8: Stop the program.

PROGRAM:

#include<stdio.h>

#include<math.h>

#include<graphics.h>

#include<conio.h>

float cxl, cxr,cyt,cyb;

code(float,float);

void clip(float,float,float,float);

void rect(float,float,float,float);

void main()

{

float x1,y1,x2,y2;

int g=0,d;

initgraph(&g,&d,"c:\\tc\\bin");

settextstyle(1,0,1);

outtextxy(40,15,"BEFORE CLIPPING");

printf("\n\n\n please enter the left,bottom,right,top,of clip window");

scanf("%f%f%f%f",&cxl,&cyt,&cxr,&cyt);

rect(cxl,cyb,cxr,cyt);

getch();

printf("\n please enter the line(x1,y1,x2,y2):");

scanf("%f%f%f%f",&x1,&y1,&x2,&y2);

line(x1,y1,x2,y2);

getch();

cleardevice();

settextstyle(1,0,1);

outtextxy(40,15,"after clipping");

clip(x1,y1,x2,y2);

getch();

closegraph();

}

void clip(float x1,float y1,float x2,float y2)

{

int c,c1,c2;

float x,y;

c1=code(x1,y1);

c2=code(x2,y2);

getch();

while((c1!=0)||(c2!=0))

{

 if((c1&c2)!=0)

goto out;

c=c1;

if(c==0)

c=c2;

if((c&1)==1)

{

y=y1+(y2-y1)*(cxl-x1)/(x2-x1);

x=cxl;

}

else

if((c&2)==2)

{

 y=y1+(y2-y1)*(cxl-x1)/(x2-x1);

 x=cxr;

}

else

if((c&8)==8)

{

x=x1+(x2-x1)*(cyb-y1)/(y2-y1);

y=cyb;

}

else

if((c&4)==4)

{

x=x1+(x2-x1)*(cyt-y1)/(y2-y1);

y=cyt;

}

if(c==c1)

{

x1=x;

y1=y;

c1=code(x,y);

}

else

{

x2=x;

y2=y;

c2=code(x,y);

}

}

out : rect(cxl,cyb,cxr,cyt);

line(x1,y1,x2,y2);

}

code(float x,float y)

{

int c=0;

if(x<cxl)

c=1;

else

if(x>cxr)

c=2;

if(y<cyb)

c=c|8;

else

if(y>cyt)

c=c|4;

return c;

}

void rect(float xl,float yb,float xr,float yt)

{

line(xl,yb,xr,yb);

line(xr,yb,xr,yt);

line(xr,yt,xl,yt);

line(xl,yt,xl,yb);

}

OUTPUT

Enter the left, bottom, right ,top of clip window

200

200

400

400

enter the line coordinates

250

300

400

450