# Program of Bresenham line drawing algorithm

```# include <iostream.h>
# include <conio.h>
# include <graphics.h>
# include <math.h>
char IncFlag;
void Bresenham(int x1,int x2,int y1,int y2);
void DrawLine(int X,int Y,int End,int PInc,int NInc,int P,int XInc,int YInc);
void main()
{
int gDriver=DETECT, gMode;
int x1,x2,y1,y2;

void Bresenham(int,int,int,int);
initgraph(&gDriver,&gMode,\"c:\\\\tc\\\\bgi\");

cout<<endl<<\"x1   : \";
cin>>x1;
cout<<endl<<\"y1   : \";
cin>>y1;
cout<<endl<<\"x2   : \";
cin>>x2;
cout<<endl<<\"y2   : \";
cin>>y2;
line(320,0,320,480);
line(0,240,640,240);
Bresenham(x1,x2,y1,y2);
getch();
}

void Bresenham(int x1,int x2,int y1,int y2)
{
int S,O,End;
int P;
int dx = abs(x1 - x2);
int dy = abs(y1 - y2);
float Slope;
int PInc,NInc,XInc,YInc;
if (dx == 0)  //Slope Infinite
{
}
else
{
Slope = (float)(y1 - y2) / (x1 - x2);
if (Slope>-1 && Slope<1)
{
IncFlag = \'X\';
PInc = 2 * (dy - dx);
NInc = 2 * dy;
P = 2 * dy - dx;
if (x1>x2)
{
S = x2;
O = y2;
End = x1;
}
else
{
S = x1;
O = y1;
End = x2;
}
//            DrawLine(x,y,End,PInc,NInc,P,XInc,YInc);
}
else
{
IncFlag = \'Y\';
PInc = 2 * (dx - dy);
NInc = 2 * dx;
P = 2 * dx - dy;
if (y1 > y2)
{
O = x2;
S = y2;
End = y1;
}
else
{
O = x1;
S = y1;
End = y2;
}
}
if (IncFlag == \'X\')
putpixel(320+S,240-O,12);
else
putpixel(320+O,240-S,12);
while (S <= End)
{
S++;
if (P<0)
P = P + NInc;
else
{
P = P + PInc;
if (Slope>0.0)
O++;
else
O--;
}
if (IncFlag == \'X\')
putpixel(320+S,240-O,12);
else
putpixel(320+O,240-S,12);
}
}
}
```

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