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Vector fonts are used more often than raster ones (because they're scalable), right?

Why are they rasterised?

What is the benefit of converting vector fonts into raster fonts?

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What are you talking about exactly? Where are vector fonts rasterized? Any example? – slhck May 25 '11 at 14:06
up vote 2 down vote accepted

anything that needs to be displayed/printed would ultimately need to be rasterised as neither your display nor your printer displays things by means of vectors. rather, they display things pixel by pixel (pixel = picture element, for the matter), in a relatively raster manner

so eventually one needs to have an approximation of what the perfect curve is like in terms of pixels, either black-or-white or with some grayscale dithering.

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i see. i meant, what is the benefit of raster fonts when compared to vector fonts?? – DrStrangeLove May 25 '11 at 14:03
@DrStrangeLove There is no benefit per se, but in order to be displayed on a pixel-based display you need to rasterize fonts, because an array of pixels can't just display a vector. – slhck May 25 '11 at 14:11
Wasn't the main benefit of raster fonts the fact that they don't have to be rasterized? I'm not sure if I remember correctly, but I think that I've read somewhere that good rasterization of fonts was a major problem for some time. – AndrejaKo May 25 '11 at 15:05
Good rasterization was a major problem -- of course they solve it by including pre-made raster font in lower point settings. with raster font the font (of course) is optimized already for all available point sizes. Nowadays with these subpixel rendering (and raster font included in vector fonts for small font size as well) good rasterization is considered a solved problem... – bubu May 25 '11 at 18:29

The main benefit is that you can tweak the bitmaps very carefully for specific, often used sizes.

At larger point sizes, say at 72pt, the curves are nice and round at a distance. But once you get down to smaller sizes, say 8 pt, you get really bad aliasing and you'd want to tune more specific type things like x height and kerning and so on.

Apple fonts used to have, for a given typeface, bitmap (rasterized) fonts in specific sizes to make them look best on screen for the common sizes, and a vector font for all other sizes. So you'd look at the font package, see 10pt, 12pt, and a TrueType font package for the typeface. Finetuning the bitmap used to make a bit more sense when everyone had the same display and the same printer resolution. Not sure how useful it is now in the age of the Retina Display.

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A vector font has to go through a rasterization process in order to be displayed. This involves "drawing" the font on a bitmap within a section of memory (memory directly connected to the screen or other intermediate memory buffer) which takes time.

With a rasterized font, it's been drawn already (rasterized fonts are just collections of bitmaps), so it just needs to be copied (and scaled) to its final destination.

So rasterized fonts, especially ones that don't have to be scaled (i.e. being viewed at their "native" size), will render faster.

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