Clip Lines - Cohen-Sutherland Line Clipping Algorithm - C++ Program - Graphics & Multimedia Lab

Cohen-Sutherland Line Clipping Algorithm

  C++ program - Graphics & Multimedia Lab

Sourcecode:

#include<graphics.h>

#include<iostream>

using namespace std;





#define MAX1 20



enum { TOP = 0x8, BOTTOM = 0x4, RIGHT = 0x2, LEFT = 0x1 };



enum { FALSE, TRUE };

typedef unsigned int outcode;

int m=0;

    FILE *ip,*op;

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 (float x1, float y1, float x2, float y2, float xmin, float ymin, float xmax, float 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;

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

     int outcode_ex = outcode1 ? outcode1 : outcode2;

     if (outcode_ex & TOP)

     {

  x = x1 + (ymax - y1)/m;

  y = ymax;

     }



     else if (outcode_ex & BOTTOM)

     {

  x = x1 + (ymin - y1) /m;

  y = ymin;

     }

     else if (outcode_ex & RIGHT)

     {

  y = y1 + (xmax - x1)* m;

  x = xmax;

     }

     else

     {

  y = y1 + (xmin - x1)* m;

  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)

   {

 fprintf(op,"\nx[%d] y[%d] x[%d] y[%d]=%.3f %.3f %.3f %.3f:(clipped line)",m,m,m+1,m+1,x1,y1,x2,y2);

 m=m+2;

 line (x1, y1, x2, y2);

   }

   else if((accept == FALSE) && (done == TRUE))

   {

   fprintf(op,"\nThe line (%.3f,%.3f),(%.3f,%.3f)is trivially rejected.",x1,y1,x2,y2);

   }

}

int main()

{

    int n;

    int i, j;

    int ln[MAX1][4];

    int clip[4];

    int gd = DETECT, gm;





   ip=fopen("csinput.txt","r");

   op=fopen("csoutput.txt","w");

    fscanf (ip,"%d", &n);

    for (i=0; i<n; i++)

 for (j=0; j<4; j++)

     fscanf (ip,"%d", &ln[i][j]);



    for (i=0; i<4; i++)

    fscanf (ip,"%d", &clip[i]);



    initgraph (&gd, &gm, NULL);



    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();

    printf("AFTER CLIPPING");

    rectangle (clip[0], clip[1], clip[2], clip[3]);

    fprintf(op,"OUTPUT POINTS\n");

    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();

    return 0;

}

Output:

nn@linuxmint ~ $ g++ lab7.cpp -lgraph
nn@linuxmint ~ $ ./a.out

"csinput.txt"

4

40 40  125 220

10 10 40 210

75 80 175 175

60 230 210 45


55 55 200 2005 

"csoutput.txt"

OUTPUT POINTS

x[0] y[0] x[1] y[1]=55.000 71.765 115.556 200.000:(clipped line)
The line (10.000,10.000),(40.000,210.000)is trivially rejected.