Imaging concepts: Anti Aliasing

Imagine that you are drawing a triangle across an image (or on the screen for that matter). The triangle is sometimes going to cross pixels in a way which makes them not totally turned on. Have a look at the figure below to see what I mean…

If we only have a black and white image, then we’ll end up with an image like the one in the figure below. I am sure you’ll agree that this isn’t a very good representation of the side of the triangle.

Anti-aliasing is when we try to correct for this problem by inserting some gray pixels. In the figure below, we have given some of the pixels a gray value which is based on how much of the pixel is “filled” with the triangle.

The triangle might be a little clearer without the grid lines.

If you compare that with the triangle we started with above, then you can see the obvious difference.

So, in summary, anti-aliasing is the process of turning on some extra gray scale pixels to improve the look of shapes we are drawing… Now, whether you actually like anti aliasing or not is another matter. A lot of people, especially those with LCD screens, complain that anti aliased text is “fuzzy” and hard to read. That’s the reason you can turn anti aliasing off in more recent versions of Microsoft Windows.

[tags: tutorial antialias]