# Program to fill a Rectangle using Scan-Line Rectangle Fill Algorithm

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

void show_screen( );

void Fill_rectangle(const int,const int,const int,const int);

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

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

int x_1=0;
int y_1=0;

int x_2=0;
int y_2=0;

do
{
show_screen( );

gotoxy(8,10);
cout<<\"Coordinates of Left Point (x1,y1) :\";

gotoxy(8,11);
cout<<\"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ\";

gotoxy(12,13);
cout<<\"Enter the value of x1 = \";
cin>>x_1;

gotoxy(12,14);
cout<<\"Enter the value of y1 = \";
cin>>y_1;

gotoxy(8,18);
cout<<\"Coordinates of Right Point (x2,y2) :\";

gotoxy(8,19);
cout<<\"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ\";

gotoxy(12,21);
cout<<\"Enter the value of x2 = \";
cin>>x_2;

gotoxy(12,22);
cout<<\"Enter the value of y2 = \";
cin>>y_2;

int driver=VGA;
int mode=VGAHI;
int error_code;

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

setcolor(15);
Rectangle(x_1,y_1,x_2,y_2);

setcolor(9);
Fill_rectangle((x_1+1),(y_1+1),(x_2-1),(y_2-1));

setcolor(15);
outtextxy(110,460,\"Press <Enter> to continue or any other key to exit.\");

int key=int(getch( ));

if(key!=13)
break;
}
while(1);

return 0;
}

//-------------------------  Fill_rectangle( )  -------------------------//

void Fill_rectangle(const int x_1,const int y_1,const int x_2,const int y_2)
{
int y_min=((y_1>=y_2)?y_2:y_1);
int y_max=((y_1<=y_2)?y_2:y_1);

for(int count=y_min;count<=y_max;count++)
Line(x_1,count,x_2,count);
}

//---------------------------  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( )
{
restorecrtmode( );
textmode(C4350);

cprintf(\"\\n********************************************************************************\");
cprintf(\"*******************-                                      -*********************\");
cprintf(\"*------------------- \");

textbackground(1);
cprintf(\" Scan-Line Rectangle Fill Algorithm \");
textbackground(8);

cprintf(\" ---------------------*\");
cprintf(\"*******************-                                      -*********************\");
cprintf(\"*-****************************************************************************-*\");

for(int count=0;count<42;count++)
cprintf(\"*-*                                                                          *-*\");

gotoxy(1,46);
cprintf(\"*-****************************************************************************-*\");
cprintf(\"*------------------------------------------------------------------------------*\");
cprintf(\"********************************************************************************\");

gotoxy(1,2);
}
```

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