Bresenham’s Line Algorithm

Bresenham's Line Algorithm

How about drawing lines on a computer screen? You’ve found it. This page explains Bresenham’s line algorithm, one of the most efficient digital line drawing algorithms. The Bresenham algorithm chooses which pixels to illuminate for a straight line between two points. This approach doesn’t require arithmetic skills; simply follow along and you’ll be drawing lines like a pro. Since Bresenham released his technique in 1965, computers have advanced, but it is still utilized in computer graphics, computer-aided design, and video game creation. Ready to start? Jump in!

Bresenham's Line Algorithm
Bresenham’s Line Algorithm

Bresenham’s Line Drawing Algorithm?

Computers make lines on digital displays using Bresenham’s line algorithm. A very efficient algorithm decides which pixels to plot to draw a line between two points.

Bresenham’s approach finds the line’s closest pixel using integer computations. This avoids expensive floating point operations. How it works:

Find the line’s beginning and finish (x1, y1).

Calculate line slope. Switch the start and end positions to draw the line from left to right if the slope is less than 1.

  1. Initialize algorithm variables: x = x1, y = y1, dx = x2 – x1, dy = y2 – y1, D = 2*dy – dx.
  2. Each step, plot the current point (x, y) and determine the next point using these rules:
  3. If D < 0, x = x+1, D = D+2*dy.
  4. If D > 0, x = x+1, y = y+1, and D = D + 2*(dy-dx).

Repeat step 4 until x2 is reached.

Bresenham’s technique effectively draws lines by iteratively calculating and plotting the closest points. It’s essential to computer graphics and utilized in CAD, video game creation, and more. Clever 1962 algorithm!

Understanding Bresenham’s Line Drawing Algorithm

Start with the basics to learn Bresenham’s line algorithm. An algorithm plots line pixels on a grid. It chooses which pixels to turn on to construct a line between two spots.

The line plot is plotted using integer computations exclusively.Why does this matter?Because the algorithm must execute quickly, integer operations are more efficient than floating point operations.

How it works:

Start at the line’s starting point (x1, y1).We then determine the slope between the spots. The x-increment technique is used for slopes below 1. For slopes larger than 1, we use the y-increment approach.

Bresenham's Line Algorithm How it works:
Bresenham’s Line Algorithm How it works:

The x-increment algorithm:

  • To decide whether to go left or right, we check if x2 is more or less than x1.
  • We calculate dx and dy increments. dy always 1.
  • Each step activates the current pixel.
  • We increment x and y by dx and dy to the end.
  • The y-increment approach is similar but increments y by 1 and calculates dx.

Bresenham’s line algorithm can draw a line between any two grid points by repeating this process. Though simple, this technique enabled many visual applications and is still used in computer graphics today. Understanding the basics will help you appreciate this smart solution.

Steps to Bresenham’s Algorithm

Computer screen lines are drawn using Bresenham’s line algorithm. It decides which pixels to turn on to construct a line between two spots. A step-by-step explanation:

1. Find the start and end coordinates.
Points (x1, y1) and (x2, y2) These are the line’s start and end x and y coordinates.

2. Find the x-y difference.
Find dx and dy = x2 – x1 and y2 – y1. They are the horizontal and vertical distances between the points.

3. Choose the line’s direction.
More horizontal line if dx > dy. Line verticality increases when dy > dx. The line is diagonal if dx = dy.

4. Initialize x, y, and error.
X = x1, y = y1, error = dx/2. The error value determines which pixels to activate.

5. Choose right or down for the next pixel.
Turn on the pixel at (x, y) and increment x by 1 if dx > dy. Turn on the pixel at (x, y) and increase y by 1 if dy > dx.

6. Calculate new error and update x/y.
The new error is the old error minus dy or dx if incrementing x or y. Then adjust x or y.

7. Repeat steps 5 and 6 until finished.
Continue turning on pixels, updating the error, and incrementing x or y until (x2, y2).

8. You now have a line between the points!
Iterating through these steps lets you draw a smooth line between any two screen positions. Practice can make Bresenham’s algorithm second nature.

Bresenham’s Algorithm Pros and Cons

Bresenham’s line drawing approach provides several computer graphics benefits. Negatives should also be considered.


The speed of Bresenham’s algorithm is a major benefit. An integer-based approach avoids floating point numbers and trigonometric functions, which slow things down. Real-time graphics require great performance, thus this is ideal.

The Bresenham algorithm is very easy to implement. The code is simple and short. Its simplicity makes optimization and customization easy. The technique can be implemented directly with hardware logic gates.

Finally, Bresenham’s lines are attractive and uniform. Lines appear smooth and natural. Uniformity prevents jagged or uneven lines from appearing in other fundamental line drawing methods.


Bresenham’s algorithm only works for lines with a slope between 0 and 1, which is its biggest drawback. Drawing lines with slopes greater than 1 is incorrect. Steep-sloped lines require more rationale. The algorithm only supports monochrome lines. Color and anti-aliasing are not built-in. These uses require additional algorithm adaptation.

Rasterization algorithms like Bresenham’s don’t produce straight lines. Pixelation makes lines ragged at extreme zoom. Vectors are needed for smooth lines. The algorithm is quick but not the most efficient for drawing lines on contemporary GPUs. Modern graphics hardware can work better with advanced line drawing algorithms. Bresenham’s suits simpler devices.

Bresenham’s line-drawing algorithm is useful for basic line rendering. It has limitations, and there may be better solutions based on your needs.  sufficient of its drawbacks for sophisticated use cases can be fixed with sufficient work.

Applications and Examples of Bresenham’s Line Algorithm
Bresenham’s line algorithm has various computer graphics and imaging uses. For raster display line drawing, utilize Bresenham’s algorithm.

Line Charts

A line drawing algorithm plots and connects data points in simple line charts, such those used in many data visualization tools. Line charts are drawn quickly and efficiently using Bresenham’s algorithm.


In computer animation and video game design, Bresenham’s line algorithm can draw lines between moving objects or construct wireframe models. Lines between objects are redrawn on each frame to simulate fluid movement.

Many printers, particularly earlier dot matrix printers, use line drawing algorithms to print lines on a page. Printer firmware can use Bresenham’s algorithm to create lines as the print head moves across the page.

Overall, Bresenham’s line algorithm is beneficial in computer graphics, imaging, design, data visualization, and engineering. Bresenham’s algorithm is ideal for drawing lines between two points quickly.


Bresenham’s line-drawing algorithm is explained for beginners. You can create lines on a raster display using this helpful method. Try the algorithm in your language to see the results. It may inspire new entertaining and creative coding ideas. Get out there and draw lines—programming is an adventure! After learning the basics, explore your creativity.

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