Cohen sutherland line clipping algorithm in c

Cohen Sutherland line clipping algorithm in C

Cohen-Sutherland line clipping is an algorithm used to determine the portion of a line that lies within a specified rectangular boundary, called a "clipping window". The algorithm divides the line into four regions based on its position relative to the clipping window, and then performs different operations depending on which region the line belongs to.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <graphics.h>
#include <dos.h>

typedef struct coord {
    int x, y;
    char code[4];
} PT;

void drawwindow();
void drawline(PT p1, PT p2);
PT setcode(PT p);
int visibility(PT p1, PT p2);
PT resetendpt(PT p1, PT p2);

void main()
{
    int gd = DETECT, v, gm;
    PT p1, p2, p3, p4, ptemp;

    printf("\nEnter x1 and y1\n");
    scanf("%d %d", &p1.x, &p1.y);
    printf("\nEnter x2 and y2\n");
    scanf("%d %d", &p2.x, &p2.y);

    initgraph(&gd, &gm, "c:\\turboc3\\bgi");
    drawwindow();
    delay(500);

    drawline(p1, p2);
    delay(500);
    cleardevice();

    delay(500);
    p1 = setcode(p1);
    p2 = setcode(p2);
    v = visibility(p1, p2);
    delay(500);

    switch (v) {
    case 0:
        drawwindow();
        delay(500);
        drawline(p1, p2);
        break;
    case 1:
        drawwindow();
        delay(500);
        break;
    case 2:
        p3 = resetendpt(p1, p2);
        p4 = resetendpt(p2, p1);
        drawwindow();
        delay(500);
        drawline(p3, p4);
        break;
    }

    delay(5000);
    closegraph();
}

void drawwindow()
{
    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)
{
    line(p1.x, p1.y, p2.x, p2.y);
}

PT setcode(PT p) //for setting the 4 bit code
{
    PT ptemp;

    if (p.y < 100)
        ptemp.code[0] = '1'; //Top
    else
        ptemp.code[0] = '0';

    if (p.y > 350)
        ptemp.code[1] = '1'; //Bottom
    else
        ptemp.code[1] = '0';

    if (p.x > 450)
        ptemp.code[2] = '1'; //Right
    else
        ptemp.code[2] = '0';

    if (p.x < 150)
        ptemp.code[3] = '1'; //Left
    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:

Enter x1 and y1
100
100

Enter x2 and y2
200
200

Before and After Clipping: