Program to fill different types of geometric shapes using Boundary Fill Algorithm

``` # include <iostream.h>
# include <graphics.h>
# include    <conio.h>
# include     <math.h>

void show_screen( );

void Boundary_fill(const int,const int,const int,const int);

void Circle(const int,const int,const int);
void Triangle(const int,const int,const int,const int,const int,const int);
void Rectangle(const int,const int,const int,const int);
void Polygon(const int,const int []);
void Line(const int,const int,const int,const int);

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

initgraph(&driver,&mode,\"..\\\\Bgi\");

show_screen( );

setcolor(15);
Circle(175,175,40);

Boundary_fill(175,175,10,15);

setcolor(15);
settextstyle(0,0,1);
outtextxy(150,225,\"Circle\");

setcolor(15);
Rectangle(375,145,475,205);

Boundary_fill(400,175,9,15);

setcolor(15);
settextstyle(0,0,1);
outtextxy(390,215,\"Rectangle\");

setcolor(15);
Triangle(135,360,215,360,175,290);

Boundary_fill(175,325,8,15);

setcolor(15);
settextstyle(0,0,1);
outtextxy(145,370,\"Triangle\");

int polygon_points[14]={ 365,325, 400,290, 450,290, 485,325,
450,360, 400,360, 365,325 };

setcolor(15);
Polygon(7,polygon_points);

Boundary_fill(425,325,12,15);

setcolor(15);
settextstyle(0,0,1);
outtextxy(395,370,\"Polygon\");

getch( );
return 0;
}

//--------------------------  Boundary_fill( )  -------------------------//

void Boundary_fill(const int x,const int y,
const int fill_color,const int boundary_color)
{
if(getpixel(x,y)!=boundary_color && getpixel(x,y)!=fill_color)
{
putpixel(x,y,fill_color);

Boundary_fill((x+1),y,fill_color,boundary_color);
Boundary_fill((x-1),y,fill_color,boundary_color);
Boundary_fill(x,(y+1),fill_color,boundary_color);
Boundary_fill(x,(y-1),fill_color,boundary_color);
}
}

//------------------------------  Circle( )  ----------------------------//

void Circle(const int h,const int k,const int r)
{
int color=getcolor( );

int x=0;
int y=r;
int p=(1-r);

do
{
putpixel((h+x),(k+y),color);
putpixel((h+y),(k+x),color);
putpixel((h+y),(k-x),color);
putpixel((h+x),(k-y),color);
putpixel((h-x),(k-y),color);
putpixel((h-y),(k-x),color);
putpixel((h-y),(k+x),color);
putpixel((h-x),(k+y),color);

x++;

if(p<0)
p+=((2*x)+1);

else
{
y--;
p+=((2*(x-y))+1);
}
}
while(x<=y);
}

//----------------------------  Triangle( )  ----------------------------//

void Triangle(const int x_1,const int y_1,const int x_2,const int y_2,
const int x_3,const int y_3)
{
Line(x_1,y_1,x_2,y_2);
Line(x_2,y_2,x_3,y_3);
Line(x_3,y_3,x_1,y_1);
}

//---------------------------  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);
}

//-----------------------------  Polygon( )  ----------------------------//

void Polygon(const int n,const int coordinates[])
{
if(n>=2)
{
Line(coordinates[0],coordinates[1],
coordinates[2],coordinates[3]);

for(int count=1;count<(n-1);count++)
Line(coordinates[(count*2)],coordinates[((count*2)+1)],
coordinates[((count+1)*2)],
coordinates[(((count+1)*2)+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(220,26,420,38);

settextstyle(0,0,1);
setcolor(15);
outtextxy(5,5,\"******************************************************************************\");
outtextxy(5,17,\"*-**************************************************************************-*\");
outtextxy(5,29,\"*-------------------------                           ------------------------*\");
outtextxy(5,41,\"*-**************************************************************************-*\");
outtextxy(5,53,\"*-**************************************************************************-*\");

setcolor(11);
outtextxy(228,29,\"Boundary Fill Algorithm\");

setcolor(15);

for(int count=0;count<=30;count++)
outtextxy(5,(65+(count*12)),\"*-*                                                                        *-*\");

outtextxy(5,438,\"*-**************************************************************************-*\");
outtextxy(5,450,\"*-------------------------                          -------------------------*\");
outtextxy(5,462,\"******************************************************************************\");

setcolor(12);
outtextxy(229,450,\"Press any Key to exit.\");
}
```

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