A CPP program to show demo on Line clip

#include<graphics.h>
#include<conio.h>
#include<iostream.h>
struct Point
{
int x,y;      // for storing x&y co-ordinates of a point
unsigned int code[4];     // to store 4digit code for a point
};
struct Line
{
Point a,b;   // Line has two points
};
Point wmin,wmax; // to store windows min& max co-ordinates
int xc,yc;    // to store maxx,maxy
void changePts(Point*,float); // func that finds intersection points of line on windows
void getCode(Point*);   // func to get the 4 digit code for a point
int getAttr(Line);  // func that decides whether to clip the line or not
void main()
{
int i,n,gd=0,gm,chk=0;
float s; //to store slope when required
Line m[10]; // to store points of Lines
initgraph(&gd,&gm,"c:\\tc\\bgi");  //initiates graphics mode
xc=getmaxx()/2,yc=getmaxy()/2;  // to get x&y centers
line(xc,0,xc,2*yc),line(0,yc,2*xc,yc);  // to draw axis lines
cout<<"\n Enter no of lines : ";
cin>>n;     //to accept no of lines
cout<<"\n Enter Co-ordinates : ";
for(i=0;i<n;i++)    // to accept end points for given n lines
cin>>m[i].a.x>>m[i].a.y>>m[i].b.x>>m[i].b.y;
cout<<"\n Enter windows min&max co-ordinates : ";
cin>>wmin.x>>wmin.y>>wmax.x>>wmax.y;  //to accept windows min&max co-ordinates
rectangle(xc+wmin.x,yc-wmin.y,xc+wmax.x,yc-wmax.y); // to draw window
for(i=0;i<n;i++)// to draw the given n lines & also find 4digit code for each point
{
line(xc+m[i].a.x,yc-m[i].a.y,xc+m[i].b.x,yc-m[i].b.y);
getCode(&(m[i].a)),getCode(&(m[i].b)); // to find 4digit code
}
for(i=0;i<n;i++)  // for clipping the lines
if(getAttr(m[i])==1)//to decide whether to clip the lines or leave it
{  //alone (if iniside) completely remove the lines (if outside)
if(m[i].a.x==m[i].b.x) // clipping of lines if slope is infinite
{
if(m[i].a.code[3]==1)
m[i].a.y=wmax.y;
else if(m[i].a.code[2]==1)
m[i].a.y=wmin.y;
if(m[i].b.code[3]==1)
m[i].b.y=wmax.y;
else if(m[i].b.code[2]==1)
m[i].b.y=wmin.y;
}
else // clipping of lines
{  start : chk++;
// for calc the slope of line
float s = float((m[i].b.y-m[i].a.y))/(m[i].b.x-m[i].a.x);

// for finding intersection point and replacing the
// present co-ordinates and finding codes for new co-ordinates
changePts(&(m[i].a),s),getCode(&(m[i].a));
changePts(&(m[i].b),s),getCode(&(m[i].b));

if(getAttr(m[i])==1&&chk<2) // checking if line is clipped completly
goto start;  // if not clipped repeat the process
if(chk==2) //chk is to take care that the clipping process
{    chk=0; goto end; }//is not repeated more than 2 times
// if its so line is to be removed completely
}
}
else  // for removing lines completely
{   end :
int d=0;
for(int j=0;j<n;j++)  //finding if line is completely inside
if(m[i].a.code[i]!=0||m[i].b.code[i]!=0)
d=1;
if(d==1) // if line is not inside
{
for(j=i;j<n-1;j++) // to remove the line
m[j]= m[j+1];
n=n-1; i--;   // to decrese no of lines
}
}
getch();
cleardevice();  // clearing screen
line(xc,0,xc,2*yc),line(0,yc,2*xc,yc); // draw axis
rectangle(xc+wmin.x,yc-wmin.y,xc+wmax.x,yc-wmax.y);//draw windows
for(i=0;i<n;i++)// drawing lines with the changed co-ordinates
line(xc+m[i].a.x,yc-m[i].a.y,xc+m[i].b.x,yc-m[i].b.y);
getch();
closegraph(); //closing graphics mode
}
void getCode(Point *a)  //to get 4digit code
{
if(a->x<wmin.x)
a->code[0]=1;
else  a->code[0]=0;
if(a->x>wmax.x)
a->code[1]=1;
else a->code[1]=0;
if(a->y<wmin.y)
a->code[2]=1;
else a->code[2]=0;
if(a->y>wmax.y)
a->code[3]=1;
else a->code[3]=0;
}
int getAttr(Line m)  //to decide whether to clip the lines or leave it
{          //alone (if iniside) completely remove the lines (if outside)
int a=1,b=0;
for(int i=0;i<4;i++)
if(m.a.code[i]&m.b.code[i]!=0)
a=0;
if(m.a.code[i]!=0||m.b.code[i]!=0)
b=1;
if(a==0||b==0)
return 0;
return 1;
}
void changePts(Point *a,float s) // for finding intersection point and
{ //replacing the present co-ordinates and finding codes for new co-ordinates
if(a->code[0]==1)
a->y+=(wmin.x-a->x)*s,a->x=wmin.x;
else if(a->code[1]==1)
a->y+=(wmax.x-a->x)*s,a->x=wmax.x;
else if(a->code[2]==1)
a->x+=(wmin.y-a->y)/s,a->y=wmin.y;
else if(a->code[3]==1)
a->x+=(wmax.y-a->y)/s,a->y=wmax.y;
}  //   SSR