CG 2

 Write C++ program to implement Cohen Southerland line clipping algorithm.

The code for above problem is as follows:

 //cohen-sutherland line clipping algorithm  
 #include<iostream.h>  
 #include<stdlib.h>  
 #include<math.h>  
 #include<graphics.h>  
 #include<dos.h>  
   
 typedef struct coordinate  
 {  
      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);  
   
 int main()  
 {  
      int gd=DETECT,v,gm;  
      PT p1,p2,p3,p4,ptemp;  
   
      cout<<"\nEnter x1 and y1\n";  
      cin>>p1.x>>p1.y;  
      cout<<"\nEnter x2 and y2\n";  
      cin>>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();  
 return 0;  
 }  
   
 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=2;  
   }  
 for(i=0;i<4;i++)  
  {  
   if((p1.code[i]==p2.code[i]) &&(p1.code[i]=='1'))  
   flag=1;  
  }  
 if(flag==0) //Line is inside window....Accept  
  return(0);  
   
 if(flag==1) //Line is outside window ...Reject  
  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;  
   
           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;  
   
           return(temp);  
      }  
      else  
           return(p1);  
 }