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# Program to draw a line using Bresenham's Line Algorithm (BLA)

Posted By: Easy Tutor     Category: C++ Programming     Views: 21832

## Code for Program to draw a line using Bresenham's Line Algorithm (BLA) in C++ Programming

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

void show_screen( );

void bresenham_line(constint,constint,constint,constint);

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 Point-I (x1,y1) :";

gotoxy(8,11);
cout<<"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ";

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 Point-II (x2,y2) :";

gotoxy(8,19);
cout<<"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ";

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

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

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

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

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;
}

/*************************************************************************///--------------------------  bresenham_line( )  ------------------------///*************************************************************************/void bresenham_line(constint x_1,constint y_1,constint x_2,constint 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(" Bresenham's Line 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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