# Implementing Bresenham’s Line Drawing Algorithm in C/C++

Bresenham’s Line Drawing Algorithm is an accurate and efficient raster line-generating algorithm developed by Bresenham. In this algorithm, we first consider the scan – conversion process for lines with positive slope less than 1. Pixel positions along a line path are then determined by sampling at unit x intervals. Starting from the left end point (x0, y0) of a given line, we step to each successive column (x position) and plot the pixel whose scan – line y values is closet to the line path. Assuming we have determined that the pixel at (x(k), y(k)) is to be displayed, we next need to decide which pixel to plot in column x(k+1). Our choices are the pixels at positions (x(k) + 1, y(k)) and (x(k) + 1, y(k) + 1).
The following section implements Bresenham’s  Algorithm in C/C++. The source code is complied using gcc Compiler and Code::Blocks IDE. To print a pixel, SetPixel() function of windows.h is used.

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### 5 Responses

1. Rajiv Mehra says:

Hey
Does Bresenham's Line Drawing Algorithm generate vertical lines?
I've tried running your code in my pc but it doesn't compile!
void drawLineBresenham(int xa, int ya, int xb, int yb){

int dx = abs(xa – xb), dy = abs(ya – yb);

int p = 2 * dy – dx;

int twoDy = 2 * dy, twoDyDx = 2 * (dy – dx);

int x, y, xEnd;

if (xa > xb){

x = xb;

y = yb;

xEnd = xa;

}else{

x = xa;

y = ya;

xEnd = xb;

}

setPixel(x, y);

while(x < xEnd){

x++;

if(p < 0)

p += twoDy;

else{

y++;

p += twoDyDx;

}

setPixel(x, y);

}

}
in verticle line x1=x2
so xend=0
🙁

2. Amit says:

I have tried this algo but doesn't run on my system.

3. Anonymous says:

So what can i do go furashole.

4. Anonymous says:

the code works on my system if i use a different putpixel function but it doesn't work correctly. it will draw lines but the two points move around when they shouldn't. i think you need to check your code. the only thing i changed was the put pixel part but nothing else.

5. Unknown says:

Doesn't work if abs(dx) > abs(dy) 