C Program For Cohen-Sutherland Line Clipping 

Source Code:

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


 -----------------  Class Declarations & Definitions  ------------------

 ---------------------------  LineCoordinates  -------------------------


 class LineCoordinates
    {
       public:
	  float x_1;
	  float y_1;
	  float x_2;
	  float y_2;

	  LineCoordinates(const float x1,const float y1,
					      const float x2,const float y2)
	     {
		x_1=x1;
		y_1=y1;
		x_2=x2;
		y_2=y2;
	     }
    };


 -------------------------  WindowCoordinates  -------------------------


 class WindowCoordinates
    {
       public:
	  float x_min;
	  float y_min;
	  float x_max;
	  float y_max;

	  WindowCoordinates(const float x1,const float y1,
					      const float x2,const float y2)
	     {
		x_min=x1;
		y_min=y1;
		x_max=x2;
		y_max=y2;
	     }
    };


 -----------------------------  RegionCode  ----------------------------


 class RegionCode
    {
       public:
	  int bit_1;
	  int bit_2;
	  int bit_3;
	  int bit_4;

	  RegionCode( )
	     {
		bit_1=0;
		bit_2=0;
		bit_3=0;
		bit_4=0;
	     }

	  const int equal_zero( )
	     {
		if(bit_1==0 && bit_2==0 && bit_3==0 && bit_4==0)
		   return 1;

		return 0;
	     }

	  void get_logical_AND(RegionCode rc1,RegionCode rc2)
	     {
		if(rc1.bit_1==1 && rc2.bit_1==1)
		   bit_1=1;

		if(rc1.bit_2==1 && rc2.bit_2==1)
		   bit_2=1;

		if(rc1.bit_3==1 && rc2.bit_3==1)
		   bit_3=1;

		if(rc1.bit_4==1 && rc2.bit_4==1)
		   bit_4=1;
	     }

	  void get_region_code(const WindowCoordinates wc,
						   const int x,const int y)
	     {
		if((wc.x_min-x)>0)
		   bit_1=1;

		if((x-wc.x_max)>0)
		   bit_2=1;

		if((wc.y_min-y)>0)
		   bit_3=1;

		if((y-wc.y_max)>0)
		   bit_4=1;
	     }
    };


 -----------------------  Function Prototypes  -------------------------


 void show_screen( );

 const int clip_line(const WindowCoordinates,LineCoordinates&);

 void calculate_intersecting_points(const WindowCoordinates,LineCoordinates&);

 void Rectangle(const int,const int,const int,const int);
 void Line(const int,const int,const int,const int);


------------------------------  main( )  ------------------------------


 int main( )
    {
       int driver=VGA;
       int mode=VGAHI;

       initgraph(&driver,&mode,"c:/tc/bgi");

       show_screen( );

       WindowCoordinates WC(180,140,470,340);

       setcolor(15);
	 Rectangle(WC.x_min,WC.y_min,WC.x_max,WC.y_max);

       LineCoordinates LC_1(150,160,120,320);
       LineCoordinates LC_2(250,150,200,200);
       LineCoordinates LC_3(160,200,490,260);
       LineCoordinates LC_4(300,300,400,380);
       LineCoordinates LC_5(550,300,450,400);
       LineCoordinates LC_6(440,110,400,370);

       setcolor(7);
	 Line(LC_1.x_1,LC_1.y_1,LC_1.x_2,LC_1.y_2);
	 Line(LC_2.x_1,LC_2.y_1,LC_2.x_2,LC_2.y_2);
	 Line(LC_3.x_1,LC_3.y_1,LC_3.x_2,LC_3.y_2);
	 Line(LC_4.x_1,LC_4.y_1,LC_4.x_2,LC_4.y_2);
	 Line(LC_5.x_1,LC_5.y_1,LC_5.x_2,LC_5.y_2);
	 Line(LC_6.x_1,LC_6.y_1,LC_6.x_2,LC_6.y_2);

       char Key=NULL;

       do
	  {
	     Key=getch( );
	  }
       while(Key!='C' && Key!='c');

       settextstyle(0,0,1);
	 setcolor(0);
	   outtextxy(163,450,"  Press 'C' to see the Clipped Lines.  ");

	setcolor(15);

	 setcolor(12);
	   outtextxy(213,450,"  Press any Key to exit.  ");

       setcolor(10);

       if(clip_line(WC,LC_1))
	  Line(LC_1.x_1,LC_1.y_1,LC_1.x_2,LC_1.y_2);

       if(clip_line(WC,LC_2))
	  Line(LC_2.x_1,LC_2.y_1,LC_2.x_2,LC_2.y_2);

       if(clip_line(WC,LC_3))
	  Line(LC_3.x_1,LC_3.y_1,LC_3.x_2,LC_3.y_2);

       if(clip_line(WC,LC_4))
	  Line(LC_4.x_1,LC_4.y_1,LC_4.x_2,LC_4.y_2);

       if(clip_line(WC,LC_5))
	  Line(LC_5.x_1,LC_5.y_1,LC_5.x_2,LC_5.y_2);

       if(clip_line(WC,LC_6))
	  Line(LC_6.x_1,LC_6.y_1,LC_6.x_2,LC_6.y_2);

       getch( );
       return 0;
    }


 ------------------------  Funcion Definitions  ------------------------

 ---------------------------  clip_line( )  ----------------------------


 const int clip_line(const WindowCoordinates wc,LineCoordinates &lc)
    {
       RegionCode rc1,rc2,rc;

       rc1.get_region_code(wc,lc.x_1,lc.y_1);
       rc2.get_region_code(wc,lc.x_2,lc.y_2);
       rc.get_logical_AND(rc1,rc2);

       if(rc1.equal_zero( ) && rc2.equal_zero( ))
	  {
	     lc.x_1=(int)(lc.x_1+0.5);
	     lc.y_1=(int)(lc.y_1+0.5);
	     lc.x_2=(int)(lc.x_2+0.5);
	     lc.y_2=(int)(lc.y_2+0.5);

	     return 1;
	  }

       else if(!rc.equal_zero( ))
	  return 0;

       else
	  {
	     calculate_intersecting_points(wc,lc);
	     clip_line(wc,lc);
	  }

       return 1;
    }


 -----------------  calculate_intersecting_points( )  ------------------


 void calculate_intersecting_points(const WindowCoordinates wc,
							LineCoordinates &lc)
    {
       RegionCode rc1,rc2,rc;

       rc1.get_region_code(wc,lc.x_1,lc.y_1);
       rc2.get_region_code(wc,lc.x_2,lc.y_2);

       if(!rc1.equal_zero( ))
	  {
	     float m;
	     float x=lc.x_1;
	     float y=lc.y_1;

	     int dx=(lc.x_2-lc.x_1);

	     if(dx!=0)
		m=((lc.y_2-lc.y_1)/(lc.x_2-lc.x_1));

	     if(rc1.bit_1==1)
		{
		   x=wc.x_min;
		   y=(lc.y_1+(m*(x-lc.x_1)));
		}

	     else if(rc1.bit_2==1)
		{
		   x=wc.x_max;
		   y=(lc.y_1+(m*(x-lc.x_1)));
		}

	     else if(rc1.bit_3==1)
		{
		   y=wc.y_min;

		   if(dx!=0)
		      x=(lc.x_1+((y-lc.y_1)/m));
		}

	     else if(rc1.bit_4==1)
		{
		   y=wc.y_max;

		   if(dx!=0)
		      x=(lc.x_1+((y-lc.y_1)/m));
		}

	     lc.x_1=x;
	     lc.y_1=y;
	  }

       if(!rc2.equal_zero( ))
	  {
	     float m;
	     float x=lc.x_2;
	     float y=lc.y_2;

	     int dx=(lc.x_2-lc.x_1);

	     if(dx!=0)
		m=((lc.y_2-lc.y_1)/(lc.x_2-lc.x_1));

	     if(rc2.bit_1==1)
		{
		   x=wc.x_min;
		   y=(lc.y_2+(m*(x-lc.x_2)));
		}

	     else if(rc2.bit_2==1)
		{
		   x=wc.x_max;
		   y=(lc.y_2+(m*(x-lc.x_2)));
		}

	     else if(rc2.bit_3==1)
		{
		   y=wc.y_min;

		   if(dx!=0)
		      x=(lc.x_2+((y-lc.y_2)/m));
		}

	     else if(rc2.bit_4==1)
		{
		   y=wc.y_max;

		   if(dx!=0)
		      x=(lc.x_2+((wc.y_max-lc.y_2)/m));
		}

	     lc.x_2=x;
	     lc.y_2=y;
	  }
    }

 ---------------------------  Rectangle( )  ----------------------------
 void Rectangle(const int x_1,const int y_1,const int x_2,const int y_2)
    {
       Line(x_1,y_1,x_2,y_1);
       Line(x_2,y_1,x_2,y_2);
       Line(x_2,y_2,x_1,y_2);
       Line(x_1,y_2,x_1,y_1);
    }
-------------------------------  Line( )  -----------------------------

 void Line(const int x_1,const int y_1,const int x_2,const int y_2)
    {
       int color=getcolor( );

       int x1=x_1;
       int y1=y_1;

       int x2=x_2;
       int y2=y_2;

       if(x_1>x_2)
	  {
	     x1=x_2;
	     y1=y_2;

	     x2=x_1;
	     y2=y_1;
	  }

       int dx=abs(x2-x1);
       int dy=abs(y2-y1);
       int inc_dec=((y2>=y1)?1:-1);

       if(dx>dy)
	  {
	     int two_dy=(2*dy);
	     int two_dy_dx=(2*(dy-dx));
	     int p=((2*dy)-dx);

	     int x=x1;
	     int y=y1;

	     putpixel(x,y,color);

	     while(x<x2)
		{
		   x++;

		   if(p<0)
		      p+=two_dy;

		   else
		      {
			 y+=inc_dec;
			 p+=two_dy_dx;
		      }

		   putpixel(x,y,color);
		}
	  }

       else
	  {
	     int two_dx=(2*dx);
	     int two_dx_dy=(2*(dx-dy));
	     int p=((2*dx)-dy);

	     int x=x1;
	     int y=y1;

	     putpixel(x,y,color);

	     while(y!=y2)
		{
		   y+=inc_dec;

		   if(p<0)
		      p+=two_dx;

		   else
		      {
			 x++;
			 p+=two_dx_dy;
		      }

		   putpixel(x,y,color);
		}
	  }
    }


 --------------------------  show_screen( )  ---------------------------


 void show_screen( )
    {
       setfillstyle(1,1);
	 bar(145,26,480,38);

       settextstyle(0,0,1);
	 setcolor(15);

	 setcolor(11);
	   outtextxy(152,29,"Cohen-Sutherland Line Clipping Algorithm");

	 setcolor(15);

	   for(int count=0;count<=30;count++)

	 setcolor(12);
	   outtextxy(163,450,"  Press 'C' to see the Clipped Lines.  ");
    }