LINE CLIPPING USING COHEN SUTHERLAND ALGORITHM

LINE CLIPPING USING COHEN SUTHERLAND ALGORITHM

#include<stdio.h>

#include<conio.h>

#include<graphics.h>

#define FALSE 0

#define TRUE 1

#define LEFTEDGE 0x1

#define RIGHTEDGE 0x2

#define TOPEDGE 0x8

#define BOTTOMEDGE 0x4

#define INSIDE(a) (!a)

#define REJECT(a,b) (a&b)

#define ACCEPT(a,b) (!(a|b))

unsigned char encode(int x,int y,int minx,int maxx,int miny,int maxy)

{

            unsigned char code=0X00;

            if(x<minx)

                        code=code|LEFTEDGE;

            if(x>maxx)

                        code=code|RIGHTEDGE;

            if(y<miny)

                        code=code|BOTTOMEDGE;

            if(y>maxy)

                        code=code|TOPEDGE;

            return(code);

}

void swappts(int *x1,int *y1,int *x2,int *y2)

{

            int tx,ty;

            tx=*x1;

            ty=*y1;

            *x1=*x2;

            *y1=*y2;

            *x2=tx;

            *y2=ty;

}

void swapcode(unsigned char *c1,unsigned char *c2)

{

            unsigned char temp;

            temp=*c1;

*c1=*c2;

*c2=temp;

}

void clipline(int minx,int maxx,int miny,int maxy,int x1,int y1,int x2,int y2)

{

            unsigned char code1,code2;

            int done=FALSE;

            int draw=FALSE;

            float m;

            while(!done)

            {

                        code1=encode(x1,y1,minx,maxx,miny,maxy);

                        code2=encode(x2,y2,minx,maxx,miny,maxy);

                        if(ACCEPT(code1,code2))

                        {

                                    done=TRUE;

                                    draw=TRUE;

                        }

                        else if(REJECT(code1,code2))

                                    done=TRUE;

                        else

                        {

                                    if(INSIDE(code1))

                                    {

                                                swappts(&x1,&y1,&x2,&y2);

                                                swapcode(&code1,&code2);

                                    }

                                    if(x2!=x1)

                                                m=(y2-y1)/(x2-x1);

                                    if(code1&LEFTEDGE)

                                    {

                                                y1+=(minx-x1)*m;

                                                x1=minx;

                                    }

                                    else if(code1&RIGHTEDGE)

                                    {

                                                y1+=(maxx-x1)*m;

                                                x1=maxx;

                                    }

                                    else if(code1&BOTTOMEDGE)

                                    {

                                                if(x2!=x1)

                                                            x1+=(miny-y1)/m;

                                                y1=miny;

                                    }

                                    else if(code1&TOPEDGE)

                                    {

                                                if(x2!=x1)

                                                x1+=(maxy-y1)/m;

                                                y1=maxy;

                                    }

                        }

            }

            if(draw)

                        line(x1,y1,x2,y2);

}

void main()

{

            int x1,x2,y1,y2,minx,miny,maxx,maxy;

            int gd=DETECT,gm;

            initgraph(&gd,&gm,"");

            printf("Enter the minimum and maximum values of x:");

            scanf("%d%d",&minx,&maxx);

            printf("Enter the minimum and maximum values of y: ");

            scanf("%d%d",&miny,&maxy);

            printf("Enter the first enpoint of line: ");

            scanf("%d%d",&x1,&y1);

            printf("Enter the second endpoint of line: ");

            scanf("%d%d",&x2,&y2);

            printf("BEFORE CLIPPING");

            rectangle(minx,maxy,maxx,miny);

            line(x1,y1,x2,y2);

            getch();

            clrscr();

            printf("AFTER CLIPPING");

            rectangle(minx,maxy,maxx,miny);

            clipline(minx,maxx,miny,maxy,x1,y1,x2,y2);

            getch();

            closegraph();

}

OUTPUT:-

           

            Enter the minimum and maximum values of x: 300  400

            Enter the minimum and maximum values of y: 300  400

            Enter the first endpoint  of line: 275  300

            Enter the second endpoint of line: 350  420

            BEFORE CLIPPING

           

                                                                               

 AFTER CLIPPING