Cohen-Sutherland Algorithm

This program is for implementing Cohen-Sutherland Line Clipping. This is a part of Mumbai University MCA Colleges Computer Graphics CG MCA Sem 2

#include<conio.h>
#include<stdio.h>
#include<graphics.h>
#include<math.h>

typedef unsigned char BYTE;

BYTE pointcheck(int x, int y);
BYTE bit1check(int p);
BYTE bit2check(int p);
BYTE bit3check(int p);
BYTE bit4check(int p);
int endprog(void);

int main (void)
{
            int gd=VGA,gm=VGAHI;
            float x,y,xmin,ymin,xmax,ymax,xn1,xn2,yn1,yn2,x1,y1,x2,y2, m;
            int bit1,bit2,bit3,bit4, p1,p2, pointcount = 0;
            initgraph(&gd, &gm, "c:\\tc\\bgi");
            xmax = 540; ymax = 380; xmin = 100; ymin = 100;
            printf("Enter start point :");
            scanf("%f %f",&x1, &y1);
            printf("Enter end point :");
            scanf("%f %f",&x2, &y2);
            setcolor(1);
            rectangle(xmin,ymin,xmax,ymax);
            setcolor(2);
            line(x1,y1,x2,y2);
            m = (y2-y1)/(x2-x1);
            p1 = pointcheck(x1,y1);
            p2 = pointcheck(x2,y2);
            bit1=bit1check(p1);
            bit2=bit2check(p1);
            bit3=bit3check(p1);
            bit4=bit4check(p1);
            printf("Point p1 is %d = %d%d%d%d",p1,bit4,bit3,bit2,bit1);
            bit1=bit1check(p2);
            bit2=bit2check(p2);
            bit3=bit3check(p2);
            bit4=bit4check(p2);
            printf("\nPoint p2 is %d = %d%d%d%d",p2,bit4,bit3,bit2,bit1);
            if (bit1check(p1)&bit1check(p2)==1) endprog();
            if (bit2check(p1)&bit2check(p2)==1) endprog();
            if (bit3check(p1)&bit3check(p2)==1) endprog();
            if (bit4check(p1)&bit4check(p2)==1) endprog();
            if(p1 == 0 & p2 == 0)
            {
                        printf("\nLine lies within the window");
                        getch();
                        return 0;
            }
            else
                        printf("\nClipping......");
            if (pointcheck(x1,y1)==0)
            {
                        xn1 = x1; yn1 = y1;
                        pointcount = pointcount + 1;
                        p1 = p2;
            }
            if (bit1check(p1) == 1)
{
                        x = xmin;
                        y = y1 + m * (xmin - x1);
                        putpixel(x,y,3);
                        setcolor(3);
                        circle(x,y,4);
                        if (pointcount > 0)
                                    xn2 = x; yn2 = y;
                        else
                        {
                                    xn1 = x; yn1 = y;
                                    pointcount = pointcount +1;
                        }
                        p1 = p2;
            }
            if (bit2check(p1) == 1)
            {
                        x = xmax;
                        y = y1 + m * (xmax - x1);
                        putpixel(x,y,3);
                        setcolor(3);
                        circle(x,y,4);
                        if (pointcount > 0)
                                    xn2 = x; yn2 = y;
                        else
                        {
                                    xn1 = x; yn1 = y;
                                    pointcount = pointcount + 1;
                        }
                        p1 = p2;
            }
            if (bit3check(p1) == 1) //it crosses ymin
            {
                        y = ymin;
                        x = x1 + (ymin - y1)/m;
                        putpixel(x,y,3);
                        setcolor(3);
                        circle(x,y,4);
                        if (pointcount > 0)
                                    xn2 = x; yn2 = y;
                        else
                        {
                                    xn1 = x; yn1 = y;
                                    pointcount = pointcount + 1;
                        }
                        p1 = p2;
            }
            if (bit4check(p1) == 1) //it crosses ymax
            {
                        y = ymax;
                        x = x1 + (ymax - y1)/m;
                        putpixel(x,y,3);
                        setcolor(3);
                        circle(x,y,4);
                        if (pointcount > 0)
                                    xn2 = x; yn2 = y;
                        else
                        {
                                    xn1 = x; yn1 = y;
                                    pointcount = pointcount + 1;
                        }
            }
            getch();
            setcolor(0);
            line (x1,y1,x2,y2);
            setcolor(4);
            line (xn1,yn1,xn2,yn2);
            getch();
            closegraph();
}
int endprog(void)
{
            printf("\nLine lies outside the window");
            getch();
            closegraph();
            return 0;
}
BYTE pointcheck(int x, int y)
{
            int val=0x00;
            if ((x - 100) < 0) val = val|0x01;            //make bit 1 --> 1
            if ((540 - x) < 0) val = val|0x02;            //make bit 2 --> 1
            if ((y - 100) < 0) val = val|0x04;            //make bit 3 --> 1
            if ((380 - y) < 0) val = val|0x08;      //make bit 4 --> 1
            return val;
}
BYTE bit1check(int a)
{
            a = a & 1;        //AND operation with 0001, making 2,3,4 bit 0
            return a;
}
BYTE bit2check(int b)
{
            b = b & 2;        //AND with 0010 i.e making 1,3,4 bit 0
            b = b >> 1;     //Right shift by 1 bit i.e cutting last digit
            return b;
}
BYTE bit3check(int c)
{
            c = c & 4;        //AND with 0100 i.e making 1,2,4 bit 0
            c = c >> 2;       //Right shift 2 dights i.e cutting last two digit
            return c;
}
BYTE bit4check(int d)
{
            d = d >> 3;      //Right shift 3 dights i.e cutting last three digit
            return d;
}





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