what’s anti-aliasing?

At a writing workshop on the weekend, we were learning about print layouts: I happened to mention “anti-aliasing”, but not everyone had heard of it. In this short post, I make a fumbling attempt to explain the process.

When you try and represent something complicated in not enough pixels, you have to make it a bit fuzzy. After all, a pixel can only be a single colour. The sharp, jagged edges you end up with are called aliasing.

To prevent the sharp edges, a graphics program will pick a colour that best approximates what’s happening in that part of the image: you end up with a somewhat blurry image that approximates the original.

If you squint at the top half of this image, you can tell what the original looked like.

antialiasing.jpg

Anti-aliasing also becomes an issue when trying to put text onto the screen. Fonts have often been prepared with printing in mind. Printing involves a lot more dots on the page than you would have pixels on screen.

text-sample.gif

Instead of using just black pixels to display black text, the computer uses anti-aliasing calculations to work out what shades of grey would best represent the font.

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