1. Program to implement the bresenhm's line algorithm to generate a line with any slope. Implement the polyline command using this algo as a routine that displays the set of straight lines between the 'n' input points. for n=1, the routine displays a single point.

/* PROGRAM #1 - Bresenhan's Polyline */

#include
#include

int x[20],y[20],dx,dy,maxx,maxy;

void exchange(int *,int *);
void setpixel(int,int,int);
void linebres(int,int,int,int);

void exchange(int *v1,int *v2)
{
 int temp;

 temp = *v1;
 *v1  = *v2;
 *v2  = temp;
}

void setpixel(int x,int y,int sgrtr1)
{
 if(sgrtr1)
	exchange(&x,&y);
 putpixel(x,y,15);
}

void linebres(int xa,int ya,int xb,int yb)
{
 int slope_type,sgrtr1=0,p;

 dx= abs(xa - xb);
 dy= abs(ya - yb);
 if(dy  dx)
	sgrtr1 = 1;
 if(sgrtr1)
 {
  exchange(&dx,&dy);
  exchange(&xa,&ya);
  exchange(&xb,&yb);
 }
 p = 2 * dy - dx;
 if(xa  xb)		       /* Make (Xb,Yb) as the starting point */
 {
  exchange(&xa,&xb);
  exchange(&ya,&yb);
 }
 slope_type = (yb  ya) ? 1 : -1;
 setpixel(xa,ya,sgrtr1);
 while(xa <0)
	p = p + 2 * dy;		/* Next point is (Xi+1,Yi)         */
   else
   {
    ya = ya + slope_type;
    p = p + 2 * (dy - dx);      /* Next point is (Xi+1,Yi+1)       */
   }
   setpixel(xa,ya,sgrtr1);
 }				/* End While construct 		   */
}				/* End Function        		   */

void main()
{
 int gd = DETECT,gm,i,n;

 initgraph(&gd, &gm, "");
 cleardevice();
 printf("Enter the number of points : ");
 scanf("%d",&n);
 for(i = 0; i >< n; i++)
 {
  printf("Enter the co-ordinates of point %d : ",i+1);
  scanf("%d %d",&x[i],&y[i]);
 }
 cleardevice();
 maxx = getmaxx() / 2;
 maxy = getmaxy() / 2;
 line(0,maxy,getmaxx(),maxy);        /* Draws X axis */
 line(maxx,0,maxx,getmaxy());        /* Draws Y axis */
 if(n == 1)
	putpixel(maxx + x[0],maxy - y[0],4);
 else
  for(i = 0; i < n-1; i++)
     linebres(maxx + x[i],maxy - y[i],maxx + x[i + 1],maxy - y[i + 1]);
 getch();
}

/* PROGRAM #2 - Bresenham's Line Thickness */

#include
#include

int x[20],y[20],dx,dy;

void exchange(int *,int *);
void setpixel(int,int,int);
void linebres(int,int,int,int);

void exchange(int *v1,int *v2)
{
 int temp;

 temp = *v1;
 *v1 = *v2;
 *v2 = temp;
}

void setpixel(int x,int y,int sgrtr1)
{
 if (sgrtr1)
	exchange(&x,&y);
 putpixel(x,y,15);
}

void linebres(int xa,int ya,int xb,int yb)
{
 int slope_type,sgrtr1 = 0,p;

 dx = abs(xa - xb);
 dy = abs(ya - yb);
 if(dy  dx)
	sgrtr1 = 1;
 if(sgrtr1)
 {
  exchange(&dx,&dy);
  exchange(&xa,&ya);
  exchange(&xb,&yb);
 }
 p = 2 * dy - dx;
 if(xa  xb)			/* Make (Xb,Yb) as the starting point */
 {
  exchange(&xa,&xb);
  exchange(&ya,&yb);
 }
 slope_type = (yb  ya) ? 1 : -1;
 setpixel(xa,ya,sgrtr1);
 while(xa <0)
	p = p + 2 * dy;		/* Next point is (Xi+1,Yi)         */
  else
  {
   ya = ya + slope_type;
   p = p + 2 * (dy - dx);	/* Next point is (Xi+1,Yi+1)       */
  }
  setpixel(xa,ya,sgrtr1);
 }				/* End While construct */
}				/* End_function */

void main()
{
 int gd = DETECT, gm,i,n,thick,j,maxx,maxy;

 initgraph(&gd, &gm, "");
 cleardevice();
 printf("Enter the number of points : ");
 scanf("%d",&n);
 for(i = 0; i >< n; i++)
 {
  printf("Enter the co-ordinates of point %d : ",i+1);
  scanf("%d %d",&x[i],&y[i]);
 }
 printf("Enter the thickness of the line :");
 scanf("%d",&thick);
 cleardevice();
 maxx = getmaxx() / 2;
 maxy = getmaxy() / 2;
 line(0,maxy,getmaxx(),maxy);		/* Draws X axis */
 line(maxx,0,maxx,getmaxy());           /* Draws Y axis */
 if(n == 1)
	putpixel(maxx + x[0],maxy - y[0],4);
 else
  for(j = 1; j <= thick; j++)
     for(i = 0;i < n-1; i++)
	 linebres(maxx+x[i]+j,maxy-y[i]+j,maxx+x[i+1]+j,maxy-y[i+1]+j);
 getch();	/* Add 'j' to all the coordinates	*/
}

/* PROGRAM #3 - Bar Graph */

#include
#include

#define lr 0
#define lc 0
#define hr 479
#define hc 639

struct eachvalue
{
 int val,barhigh;
 char label[20];
} item[100];

void Bar(int sc,int sr,int ec,int er)
{
 line(sc,sr,sc,er);
 line(sc,sr,ec,sr);
 line(ec,sr,ec,er);
}

void showgraph(int n,int neg)
{
 int i,hor,bstart = 80,thick = 450 / n;
 char str[80],temp[80];

 hor = (neg) ? 226 : 452;      /* If the graph has - ve values then  */
 setcolor(GREEN);	  /* draw the X axis in the middle of the screen.*/
 line(15,hor,hc - 15,hor);	                 /* Draws the X axis   */
 line(bstart - 15,lr + 15,bstart - 15,hr - 15);  /* Draws Y axis       */

 for (i=0;i<n;i++)
 {
  itoa(item[i].val,str,10);            /* Stores values in 'str' */
  setcolor(RED);
  Bar(bstart,hor - item[i].barhigh,bstart + thick,hor);
						       /* Draws bar      */
  setcolor(WHITE);
  settextstyle(2,1,6);
  if (item[i].val  = 0)
   outtextxy(bstart+(thick-20)/2,hor-10-10*strlen(item[i].label),item[i].label);
  else                                                 /* Displays Label */
   outtextxy(bstart+(thick-20)/2,hor+10,item[i].label);

  settextstyle(2,0,6);
  setcolor(YELLOW);
  outtextxy(bstart+2,hor-item[i].barhigh-((item[i].val=0) ? 20 : 0),str);
  bstart += thick + 3;               /* Displays values of each bar */
 }		       		     /* End for loop construct	    */
 settextstyle(2,0,5);
 setcolor(MAGENTA);
 itoa(0,str,10);
 outtextxy(lc+20,hor,str);           /* Displays the Origin 	    */
}

void main()
{
 int n,gd = DETECT,gm,i;
 int scale,maxval = 0,neg = 0,npar;

 clrscr();
 printf("\nEnter the number of entries : ");
 scanf("%d",&n);
 for (i=0;i<n;i++)
 {
  printf("Enter the Value and Label for item %d :\n",i+1);
  scanf("%d %s",&item[i].val,&item[i].label);
  if (abs(item[i].val)  maxval)
		maxval = abs(item[i].val);
  if (item[i].val <0)
		neg = 1;   /* Indicates Bars with -ve height are present */
 }
 npar = (neg) ? 5 : 10;
 scale = (maxval / npar) + ((maxval % 10) ? 1 : 0);
 for (i=0;i><n;i++)
	item[i].barhigh = ((float) item[i].val / scale) * 40;
 initgraph(&gd,&gm,"");      /* Finds the barheight using the values  */
 cleardevice();		     /* entered and does scaling.	      */
 showgraph(n,neg);
 getch();
 closegraph();
}

/* PROGRAM #4 - Line Graph */

#include
#include

#define lr 0
#define lc 0
#define hr 479
#define hc 639

struct eachvalue
{
 int val,barhigh;
 char label[20];
} item[100];

void polyline(int x[],int y[],int n,int color)
{
 int i;

 setcolor(color);
 if (n == 1)
   putpixel( *x, *y,color);
 else
   for (i=0;i<n-1;i++)
       line(x[i],y[i],x[i+1],y[i+1]);
}

void showgraph(int n,int neg)
{
 int i,hor,bstart = 80,thick = 450 / n,x[10],y[10];
 char str[80],temp[80];

 hor = (neg) ? 226 : 452;      /* If the graph has - ve values then  */
 setcolor(GREEN);	   /* draw the X axis in the middle of the screen.*/
 line(15,hor,hc-15,hor);      			/* Draws the X axis   */
 line(bstart-15,lr+15,bstart-15,hr-15); 	/* Draws Y axis       */

 for (i=0;i<n;i++)
 {
  itoa(item[i].val,str,10);
  x[i] = bstart + thick / 2;
  y[i] = hor - item[i].barhigh;

  setcolor(5);
  outtextxy(x[i]-3,y[i]-6,"*");

  setcolor(WHITE);
  settextstyle(2,1,4);                    /* Displays the Label */
  if (item[i].val  = 0)
   outtextxy(bstart+(thick-20)/2,hor-1*strlen(item[i].label),item[i].label);
  else
   outtextxy(bstart+(thick-20)/2,hor+10,item[i].label);

  settextstyle(2,0,6);                  /* Displays the values    */
  setcolor(YELLOW);
  outtextxy(bstart+2,hor-item[i].barhigh-((item[i].val=0)?20:0),str);
  bstart += thick + 3;
 }					/* End For Loop construct */
 polyline(x,y,n,11);
 settextstyle(2,0,5);
 setcolor(MAGENTA);
 itoa(0,str,10);
 outtextxy(lc + 20,hor,str);	        /* Displays the Origin    */
}

void main()
{
 int n,gd = DETECT,gm,i;
 int scale,maxval = 0,neg = 0,npar;

 clrscr();
 printf("Enter the number of entries : ");
 scanf("%d",&n);
 for (i=0;i<n;i++)
 {
  printf("Enter the value and label for item %d :\n",i+1);
  scanf("%d %s",&item[i].val,&item[i].label);
  if (abs(item[i].val)  maxval)
		maxval = abs(item[i].val);
  if (item[i].val <0)
		neg = 1;  /* Indicates Bars with -ve value are present */
 }
 npar = (neg) ? 5 : 10;
 scale = (maxval / npar) + ((maxval % 10) ? 1 : 0);
 for (i=0;i><n;i++)
	item[i].barhigh = ((float) item[i].val / scale) * 40;
 initgraph(&gd,&gm,"");	      /* Finds the barheight using the values  */
 cleardevice();               /* entered and does scaling.	       */
 showgraph(n,neg);
 getch();
 closegraph();
}

/* PROGRAM # 5A - Circle */

#include
#include

void plot_circle_points(int x,int y,int xc,int yc)
{
 putpixel(xc + x,yc + y, 15);
 putpixel(xc - x,yc + y, 15);
 putpixel(xc + x,yc - y, 15);
 putpixel(xc - x,yc - y, 15);
 putpixel(xc + y,yc + x, 15);
 putpixel(xc - y,yc + x, 15);
 putpixel(xc + y,yc - x, 15);
 putpixel(xc - y,yc - x, 15);
}

void bres_circle(int xc,int yc,int radius)
{
 int x = 0,y = radius,p = 3 - 2 * radius;
			   /* Select first position (Xi,Yi) as (0,r) */
 while(x <0)
	p += 4 * x + 6;	  	/* Next point is (Xi+1,Yi)   */
  else
  {
   y--;
   p += 4 * (x - y) + 10;       /* Next point is (Xi+1,Yi-1) */
  }
 }				/* End While construct 	     */
 if(x == y)
	plot_circle_points(x,y,xc,yc);
}

void main (void)
{
 int x,y,r,gd = DETECT,gm,maxx,maxy;

 initgraph(&gd,&gm,"");
 printf("Enter (xc,yc) and radius:\n");
 scanf("%d %d %d",&x,&y,&r);
 cleardevice();
 maxx = getmaxx() / 2;
 maxy = getmaxy() / 2;
 line(0,maxy,getmaxx(),maxy);      /* Draws X axis */
 line(maxx,0,maxx,getmaxy());      /* Draws Y axis */
 bres_circle(x + maxx,maxy - y,r);
 putpixel(x + maxx,maxy - y,14);   /* Draws the centre point of circle */
 getch();
 closegraph();
}
>
/* PROGRAM #5B  - Cardioid */

#include
#include
#include

void plot_circle_points(int x,int y,int xc,int yc)
{
 putpixel(xc + x,yc + y, 14);
 putpixel(xc - x,yc + y, 14);
 putpixel(xc + x,yc - y, 14);
 putpixel(xc - x,yc - y, 14);
 putpixel(xc + y,yc + x, 14);
 putpixel(xc - y,yc + x, 14);
 putpixel(xc + y,yc - x, 14);
 putpixel(xc - y,yc - x, 14);
}

void bres_circle(int xc,int yc,int radius)
{
 int x = 0,y = radius,p = 3 - 2 * radius;
			   /* Select first position (Xi,Yi) as (0,r) */
 while(x <0)
	p += 4 * x + 6;               /* Next point is (Xi+1,Yi)   */
  else
  {
   y--;
   p += 4 * (x - y) + 10;	 /* Next point is (Xi+1,Yi-1) */
  }
 }				 /* End While construct       */
 if(x == y)
	plot_circle_points(x,y,xc,yc);
}

void main (void)
{
 int x,y,r,gd = DETECT,gm,maxx,maxy;
 float s,t;
		    /* Note : 's' & 't' must always be declared as float */
 initgraph(&gd,&gm,"");
 printf("Enter (xc,yc),radius:");
 scanf("%d %d %d",&x,&y,&r);
 cleardevice();
 maxx = getmaxx() / 2;
 maxy = getmaxy() / 2;
 line(0,maxy,getmaxx(),maxy);      /* Draws X axis */
 line(maxx,0,maxx,getmaxy());      /* Draws Y axis */
 for(t = 0; t ><= 6.28; t += 0.01)
 {              		       /* s=r*t; for spiral        */
  s = r * (1 + cos(t));    	       /* s=r*cos(3*t); for 3 leaf */
  bres_circle(maxx + x + s * cos(t),maxy - y + s * sin(t),s);
  delay(15);
 }
 getch();
 closegraph();
}

/* PROGRAM #6A - Ellipse */

#include
#include

void plotpoints(float x,float y, int cx,int cy)
{
 if (x <1) x = 0;
 if (y ><1) y = 0;
 putpixel(cx + x,cy - y, 15);
 putpixel(cx - x,cy - y, 15);
 putpixel(cx + x,cy + y, 15);
 putpixel(cx - x,cy + y, 15);
}

void Ellipse(int cx,int cy,float rx,float ry)
{
 float x,y,p,endv,k;

 x = 0;  		      /* Select first point as (0,ry)   */
 y = ry;
 k = (ry * ry) / (rx * rx);
 p = 2 * k - 2 * ry + 1;      /* Initial decision parameter     */
 while(x ><-1)
	break;
  if(p ><0)
	p += 4 * k * x + 6 * k; 	  /* Next point is (Xi+1,Yi)   */
  else
  {
   p += 4 * k * x - 4 * y + 6 * k * 4;    /* Next point is (Xi+1,Yi-1) */
   y--;
  }
  x++;
 }			/* End While construct 1 */
 endv = y;
 y = 0;
 x = rx;
 k = (rx * rx) / (ry * ry);
 while(y ><0)
	p += 4 * k * y + 6 * k;
  else
  {
   p += 4 * k * y - 4 * x + 6* k + 4;
   x--;
  }
  y++;
 }			/* End While construct 2 */
}

void main (void)
{
 int ex,ey,gd = DETECT,gm,sx,sy;
 float rx,ry,r;

 initgraph(&gd,&gm,"");
 cleardevice();
 printf("\nEnter the radii(Major & Minor):\n");
 scanf("%f %f",&rx,&ry);
 printf("Enter the co-ords. of the centre:\n");
 scanf("%d %d",&ex,&ey);
 cleardevice();
 Ellipse(ex,480 - ey,rx,ry);
 getch();
 closegraph();
}
>
/* PROGRAM #6B - Spiral */

#include
#include
#include

#define PI 3.14159654

void spiral(int sx,int sy,float r)
{
 float t,s;

 for(t = 0; t <= 6 * PI; t += 0.01)
 {
  s = r * (t / (6 * PI));
  putpixel(sx + s * cos(t),sy + s * sin(t),15);
 }
}

void main (void)
{
 int gd = DETECT,gm,sx,sy;
 float r;

 initgraph(&gd,&gm,"");
 cleardevice();
 printf("\nEnter the spiral radius:");
 scanf("%f",&r);
 printf("Enter the co-ords. of the centre(Xc,Yc) :\n");
 scanf("%d %d",&sx,&sy);
 cleardevice();
 spiral(sx,480 - sy,r);
 getch();
 closegraph();
}

/* PROGRAM #7 - -rotate-translate / translate-rotate & X,Y shear */

#include 
#include 
#include 

int ps[4][2];

void translate(int q[4][2],int tx,int ty)
{
 int i;

 for(i=0;i<4;i++)
 {
  q[i][0] += tx;	/* X' = X + Tx  */
  q[i][1] += ty;	/* Y' = Y + Ty  */
 }
}

void rotate( int q[4][2],float angle)
{
 int i;			   /* X' = Xr+(X-Xr)*Cos(t) - (Y-Yr)*Sin(t) */
			   /* Y' = Yr+(X-Xr)*Sin(t) + (Y-Yr)*Cos(t) */
 angle /= (180 / 3.1415);
 for(i=0;i<4;i++)
 {
  q[i][0] = ps[3][0] + (ps[i][0]-ps[3][0])*cos(angle) - (ps[i][1]-ps[3][1])*sin(angle);
  q[i][1] = ps[3][0] + (ps[i][0]-ps[3][0])*sin(angle) + (ps[i][1]-ps[3][1])*cos(angle);
 }
}

void xshear(int p[4][2],float sh)
{
 p[2][0] += sh * ps[2][1];
 p[3][0] += sh * ps[3][1];
}

void yshear(int p[4][2],float sh)
{
 p[1][1] += sh * ps[1][0];
 p[2][1] += sh * ps[2][0];
}

void draw(int p[4][2])
{
 int i;			  /* Draws the Rectangle */

 for(i=0;i<3;i++)
	     line(p[i][0],480-p[i][1],p[i+1][0],480-p[i+1][1]);
 line(p[0][0],480-p[0][1],p[3][0],480-p[3][1]);
 getch();
}

void reset(int q[4][2])
{
 int i;

 for(i=0;i<4;i++)
 {
  q[i][0] = ps[i][0];
  q[i][1] = ps[i][1];
 }
}

void main(void)
{
 int q[4][2],i,tx,ty,gd = DETECT,gm;
 float rotn,xs,ys;

 initgraph(&gd,&gm,"");
 printf("\nEnter Top left (x1,y1) and Bottom right (x2,y2) :\n");
 scanf("%d %d",&ps[0][0],&ps[0][1]);
 scanf("%d %d",&ps[2][0],&ps[2][1]);
 ps[1][0] = ps[2][0];
 ps[1][1] = ps[0][1];
 ps[3][0] = ps[0][0];
 ps[3][1] = ps[2][1];
 printf("\nEnter the translation value across x and y axes (tx,ty) :\n");
 scanf("%d %d",&tx,&ty);
 printf("\nEnter the rotation angle in degrees:\n");
 scanf("%f",&rotn);
 printf("\nEnter the shear values across x and y axes:\n");
 scanf("%f %f",&xs,&ys);
 cleardevice();

 outtext("Rotation followed by translation");
 draw(ps);
 reset(q);
 rotate(q,rotn);
 draw(q);
 translate(q,tx,ty);
 draw(q);
 cleardevice();
 reset(q);

 outtext("Translation followed by Rotation");
 draw(ps);
 translate(ps,tx,ty);
 reset(q);
 draw(q);
 rotate(q,rotn);
 draw(q);
 cleardevice();
 reset(q);

 outtext("X and Y direction shear");
 draw(q);
 xshear(q,xs);
 draw(q);
 yshear(q,ys);
 draw(q);
 closegraph();
}

/* PROGRAM #8 - Scaling w.r.t origin,w.r.t point;Reflect about y=x */

#include
#include
#include

int ps[13][2];

void scale(int p[13][2],int fx,int fy,float sx,float sy)
{
 int i;			/* X' = Sx * X + Xr * (1 - Sx) */
			/* Y' = Sy * Y + Yr * (1 - Sy) */
 for (i=0;i<13;i++)
 {
  p[i][0] = sx * ps[i][0] + fx * (1 - sx);
  p[i][1] = sy * ps[i][1] + fy * (1 - sy);
 }
}

void reflectxy(int p[13][2])
{				/* Exchange Xi with Yi */
 int i,temp;

 for (i=0;i<13;i++)
 {
  temp = p[i][0];
  p[i][0] = p[i][1];
  p[i][1] = temp;
 }
}

void draw(int p[13][2])
{
 int i;
				/* Draws a house like figure */
 for (i = 0; i < 12; i++)
	  line(p[i][0],480 - p[i][1],p[i+1][0],480 - p[i+1][1]);
 line(p[0][0],480 - p[0][1],p[12][0],480 - p[12][1]);
 getch();
}

void reset(int q[13][2])
{
 int i;

 for (i=0;i<13;i++)
 {
  q[i][0] = ps[i][0];
  q[i][1] = ps[i][1];
 }
 cleardevice();
}

void main()
{
 int gd = DETECT,gm,x,y,i,q[13][2];
 float sx,sy;

 initgraph(&gd,&gm,"");
 ps[0][0] =  50;  ps[0][1] = 20; ps[6][0]  = 250; ps[6][1]  =  70;
 ps[1][0] = 140;  ps[1][1] = 20; ps[7][0]  = 190; ps[7][1]  =  70;
 ps[2][0] = 140;  ps[2][1] = 40; ps[8][0]  = 190; ps[8][1]  =  90;
 ps[3][0] = 160;  ps[3][1] = 40; ps[9][0]  = 150; ps[9][1]  = 130;
 ps[4][0] = 160;  ps[4][1] = 20; ps[10][0] = 110; ps[10][1] =  90;
 ps[5][0] = 250;  ps[5][1] = 20; ps[11][0] = 110; ps[11][1] =  70;
				 ps[12][0] = 50; ps[12][1]  =  70;
 printf("Enter the co-ordinates of any arbitrary point :\n");
 scanf("%d %d",&x,&y);
 printf("Enter the scaling values (Sx,Sy) along the X & Y axis :\n");
 scanf("%f %f",&sx,&sy);
 reset(q);
 draw(q);

 scale(q,50,20,sx,sy);
 outtext("Scale w.r.t Origin");
 draw(q);
 reset(q);
 draw(q);
				/* 'x' & 'y' are arbitrary points */
 scale(q,50 + x,20 + y,sx,sy);
 outtext("Scale w.r.t point entered ");
 draw(q);
 reset(q);		/* Note : cleardevice() is done in reset() */
 draw(q);

 reflectxy(q);
 outtext("Reflection about the line y = x ");
 draw(q);
 closegraph();
}

/* PROGRAM #9 - Rotate Wheel */

#include
#include
#include

void putwheel(int cx,int cy,int r,float angle)
{
 int x,y;

 circle(cx,cy,r);
 x = r * cos(angle);
 y = r * sin(angle);
 line(cx - x,cy - y,cx + x,cy + y);   /* These 2 lines draws the spokes */
 line(cx - y,cy + x,cx + y,cy - x);
 line(1,201 + r,640,201 + r);
} 		           /* Draws the Surface for the wheel to rotate */

void main(void)
{
 int gd = DETECT,gm,n,steps,r,x;
 float t;

 initgraph(&gd,&gm,"");
 printf("\nEnter the radius:");
 scanf("%d",&r);
 printf("\nEnter the number of steps:");
 scanf("%d",&steps);
 cleardevice();
 if (steps  640)
	steps = 640;
 n = 640 / steps;
 for(x = 1,t = 0.1; x < 650; t += (float) n / r)
 {
  putwheel(x,200,r,t);          /* Y coordinate remains the same (200)  */
  delay(300);			/* & only the X coordinate of the wheel */
  cleardevice();		/* is incremented,and a new wheel is    */
  x += n;			/* drawn in each loop while erasing the */
 }				/* previous image of the wheel.		*/
 putwheel(x,200,r,t);
 getch();
 closegraph();
}

/* PROGRAM #10  - Line Clipping */

#include
#include

struct eachpoint
{
 int x,y;
} pts[2],wmin,wmax,vmin,vmax,vp,vq;

int vx,vy;

void encode(struct eachpoint p,int code[4])
{
 code[0] = p.x < wmin.x;      /* Encodes the lines endpoint using */
 code[1] = p.x  wmax.x;      /* region codes.			  */
 code[2] = p.y < wmin.y;
 code[3] = p.y  wmax.y;
}

int accept(int c1[4],int c2[4])
{
 int k, acc = 1;

 for(k=0;k<4;k++)
	if(c1[k] || c2[k])
		 acc = 0;
 return acc;
}

int reject(int c1[4],int c2[4])
{
 int k,rej = 0;

 for(k=0;k<4;k++)
	if(c1[k] && c2[k])
		rej = 1;
 return rej;
}

int ptinside(int c[4])
{
 if(c[0] || c[1] || c[2] || c[3])
	return 0;
 return 1;
}

void clipline(struct eachpoint p1,struct eachpoint p2)
{
 int c1[4],c2[4],done,draw,i,t;
 float m;
 struct eachpoint tp;

 done = draw = 0;
 while(!done)		/* Repeat for all portions of line until it is */
 {			/* accepted or rejected.		       */
  encode(p1,c1);
  encode(p2,c2);
  if(accept(c1,c2))     /* If the region codes for both end points [p1,p2]*/
	done = draw = 1;    /* are zero,the line is accepted for display. */
  else if(reject(c1,c2)) /* If the region codes are 1 and the logical AND */
	done = 1;	 /* of the codes is 1 then reject the line.	  */
  else
  {
   if(ptinside(c1))
   {
    for(i=0;i<4;i++)
    {
     t = c1[i];
     c1[i] = c2[i];
     c2[i] = t;
    }
    tp = p1;
    p1 = p2;
    p2 = tp;
   }
   if ((float) (p2.x - p1.x) <1 && (float) (p2.x - p1.x) > -1)
	m = 32000;
   else						     /* 'm' is the slope */
	m = (float) (p2.y - p1.y) / (p2.x - p1.x);
   if (c1[0])			   /* LEFT		*/
   {                               /* Intersection of the first point */
    p1.y += (wmin.x - p1.x) * m;   /* with the window boundary.	      */
    p1.x = wmin.x;
   }
   else if (c1[1])                 /* RIGHT		*/
   {
    p1.y += (wmax.x - p1.x) * m;
    p1.x = wmax.x;
   }
   else if (c1[2])                 /* BOTTOM		*/
   {
    p1.x += (wmin.y - p1.y) / m;
    p1.y = wmin.y;
   }
   else if (c1[3])
   {
    p1.x += (wmax.y - p1.y) / m;   /* TOP		*/
    p1.y = wmax.y;
   }
  }		/* End Else	       */
 }		/* End While construct */
 if(draw)
 {
  line(p1.x,p1.y,p2.x,p2.y);   /* Clipped line in window */
  getch();
  cleardevice();
  vp.x = vmin.x + (p1.x-wmin.x) * (float)(vmax.x-vmin.x) / (wmax.x-wmin.x);
  vp.y = vmin.y + (p1.y-wmin.y) * (float)(vmax.y-vmin.y) / (wmax.y-wmin.y);
  vq.x = vmin.x + (p2.x-wmin.x) * (float)(vmax.x-vmin.x) / (wmax.x-wmin.x);
  vq.y = vmin.y + (p2.y-wmin.y) * (float)(vmax.y-vmin.y) / (wmax.y-wmin.y);
  outtext("Clipped line in viewport");
  line(vp.x,vp.y,vq.x,vq.y);
 }
}

void main()
{
 int i,driver = DETECT,mode,x,y;

 initgraph(&driver,&mode,"");
 printf("\nEnter the starting and ending co-ordinates of the line \n");
 scanf("%d %d %d %d",&pts[0].x,&pts[0].y,&pts[1].x,&pts[1].y);
 printf("\nEnter clip window co-ordinates (Top left & Bottom right ends)\n");
 scanf("%d %d %d %d",&wmin.x,&wmin.y,&wmax.x,&wmax.y);
 printf("\nEnter the viewport co-ordinates(Top left & Bottom right ends)\n");
 scanf("%d %d %d %d",&vmin.x,&vmin.y,&vmax.x,&vmax.y);
 cleardevice();

 outtext("ORIGINAL STATUS");
 setcolor(5);
 line(pts[0].x,pts[0].y,pts[1].x,pts[1].y);
 rectangle(wmin.x,wmin.y,wmax.x,wmax.y);
 getch();
 cleardevice();

 outtext("CLIPPED LINE IN WINDOW");
 rectangle(wmin.x,wmin.y,wmax.x,wmax.y);
 setcolor(6);
 clipline(pts[0],pts[1]);
 rectangle(vmin.x,vmin.y,vmax.x,vmax.y);   /* Draws the Viewport */
 getch();
 closegraph();
}

/* PROGRAM #11  - Sutherland-Hodgemann Polygon Clipping  */

# include 
# include 
# include 
# include 
# include 
# include 
# include 

# define TRUE 1
# define FALSE 0

typedef struct pt
{
 int x,y;
} point;

typedef enum x {LEFT,RIGHT,BOTTOM,TOP} Boundary;

int ptscnt = 0,index = 0, newboundary[4], ptsin[40],ptsout[40], n;
point WinMax,WinMin,s[4],firstpoint[4];

/* 'ptsin[]' stores the input co-ordiates of the polygon
   'ptsout[]' stores the output co-ordinates of the clipped polygon
   'ptscnt' stores the no. of points in the clipped polygon
   'WinMax','WinMin' are the co-ordinates of the window		 */

int Inside (point p,Boundary b)
{
 int flag = TRUE;

 switch(b)
 {
  case LEFT  : if (p.x  WinMax.x) flag = FALSE;
	       break;
  case BOTTOM: if (p.y  WinMax.y) flag = FALSE;
	       break;
 }
 return flag;
}

int Cross (point p1,point p2,Boundary b)
{
  if (Inside (p1,b) == Inside (p2,b))
      return FALSE;
  else
      return TRUE;
}


point Intersect(point p1,point p2,Boundary b)
{
 float m;
 point i;

 if (p1.x == p2.x)
	m = 20000;
 else
	m = (float) (p1.y-p2.y)/(p1.x-p2.x);
 switch(b)
 {
  case LEFT: i.x = WinMin.x;
	     if (p1.y == p2.y)
			i.y = p1.y;
	     else
			i.y = p2.y + (WinMin.x - p2.x) * m;
	     break;

  case RIGHT: i.x = WinMax.x;
	      if (p1.y == p2.y)
			i.y = p1.y;
	      else
			i.y = p2.y + (WinMax.x - p2.x) * m;
	      break;

  case BOTTOM: i.y = WinMin.y;
	       if (p1.x == p2.x)
			i.x = p1.x;
	       else
			i.x = p2.x + (WinMin.y - p2.y) / m;
	       break;

  case TOP: i.y = WinMax.y;
	    if (p1.x == p2.x)
			i.x = p1.x;
	    else
			i.x = p2.x + (WinMax.y - p2.y) / m;
	    break;
 }				/* End Switch construct */
 return i;
}

void ClipPoint(point p,Boundary b)
{
 point i;

 if (newboundary[b])
 {
  firstpoint[b] = p;
  newboundary[b] = FALSE;
 }
 else
 if (Cross(p,s[b],b))
 {
  i = Intersect(p,s[b],b);
  if (b <= TOP; b++)
 {
  if (Cross(s[b],firstpoint[b],b))
  {
   i = Intersect(s[b],firstpoint[b],b);
   if (b <= TOP; b++)
	newboundary[b] = TRUE;
 for (i = 0; i < n; i++)
 {
  tmp.x = ptsin[ptr++];
  tmp.y = ptsin[ptr++];
  ClipPoint(tmp,LEFT);
 }
 CloseClip();
}

void main(void)
{
 int ptr = 0,i;
 int gd = DETECT,gm;

 printf("\nEnter the no. of sides of the polygon..");
 scanf("%d",&n);
 printf("\nEnter the vertices of the polygon..");
 fflush(stdin);
 for (i=0;i<n;i++)
 {
  printf("\nVertex %d  ",i+1);
  scanf("%d %d",&ptsin[ptr++],&ptsin[ptr++]);
 }
 ptsin[ptr++] = ptsin[0];
 ptsin[ptr] = ptsin[1];
 printf("\nWindow Boundaries...\nMin x,y..");
 scanf("%d %d",&WinMin.x,&WinMin.y);		/* Min Window boundary */
 printf("\nMax x,y..");
 scanf("%d %d",&WinMax.x,&WinMax.y);		/* Max Window boundary */

 initgraph(&gd,&gm,"");
 rectangle(WinMin.x,WinMin.y,WinMax.x,WinMax.y);  /* Draw Window       */
 drawpoly(n + 1,ptsin);     /* "drawpoly()" draws the outline of a polygon */
 getch();
 cleardevice();
 PolyClip();
 ptsout[index++] = ptsout[0];
 ptsout[index++] = ptsout[1];
 drawpoly(ptscnt + 1,ptsout);
 getch();
}

/*****************************************************************************
Working
--------
enter the # of points for the polygon
then enter the x,y points for the polygon vertex by vertex
enter the min & max values for the window
finally the clipped polygon is being displayed.
*******************************************************************************/

/* PROGRAM #12  - Car  */

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

void body();
void wheel();

void main()
{
 int gd = DETECT,gm,q;

 initgraph(&gd,&gm,"");
 setbkcolor(WHITE);
 while(1)
 {
  gotoxy(1,1);
  printf("\n1.Display body of car\n2.Display Wheels\n3.Display Car\n4.Exit\n");
  q = getch();
  cleardevice();
  switch(q)
  {
   case '1' : body();
	      break;
   case '2' : wheel();
	      break;
   case '3' : body();
	      wheel();
	      break;
   case '4' : exit(0);
  }			/* End of switch(q) */
 }			/* End of While(1)  */
}			/* End of Main()    */

void body()
{
 setcolor(RED);
 line(200,200,350,200);
 line(350,200,425,250);
 line(425,250,525,275);
 line(525,275,525,325);
 line(525,325,425,325);
 line(350,325,225,325);
 line(100,325,100,250);
 line(150,250,100,250);
 line(150,325,100,325);
 line(150,250,200,200);
 arc(188,325,0,180,36);
 arc(388,325,0,180,36);
}

void wheel()
{
 setcolor(DARKGRAY);
 circle(188,325,33);
 circle(388,325,33);
 fillellipse(188,325,30,30);
 fillellipse(388,325,30,30);
}