Linked by Thom Holwerda on Tue 23rd Jun 2009 21:40 UTC
Graphics, User Interfaces The Engineering 7 weblog has an item about the improvements made in the ClearType font rendering technology which has been included in Windows since Windows XP. While I won't go too deeply into that post, I did figure it was a good opportunity to talk about font antialiasing in general; which type do you prefer?
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RISC OS fonts
by torbenm on Wed 24th Jun 2009 07:40 UTC
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I have never seen a font rendering system that beats the one on RISC OS. It is not so much the anti-aliasing over texture, it is other features:

- The same rendering engine is used for both on-screen view and print, so the screen view is print accurate (up to your screen resolution).

- It has a hinting system that I find superior to that used in Windows or MacOS fonts. For example, a hint can say that two vertical bars (like in "H") should appear identical, so you avoid one appearing thinner or more blurred than the other. I'm not that familiar with the hinting systems in ClearType or TrueType, but it doesn't look like they handle this very well.

- It works very well on low screen resolutions, partly because it had special handling of very thin lines (like the upper and lower parts of an "O" in Times Roman) that prevented gaps. My first RISC OS computer had a screen resolution of 640x256 pixels, and anti-aliasing really helped readability quite a lot, even with small fonts.

- It is fast. This might not matter much on today's computers, but when you had an 8MHz 1MB computer, it was essential.

- It is easily user-tunable. You can set the size where anti-aliasing kicks in, where sub-pixel character placement kicks in (both vertically and horisontally) and so on. This both allows quality vs. speed compromises and a degree of screen readabiliy vs. print accuracy compromise (i.e., in the sub-pixel choice).

- It uses cubic Bezier curves (like PostScript), where TrueType uses the less accurate quadratic Bezier curves.

As for print accuracy versus screen readbility in a font renderer, I favour print accuracy. I can always get better screen readbility by choosing fonts that are designed for this -- I don't edit programs or LaTeX source files in Times Roman font anyway, but if the screen renderer is not print accurate, I can't get an accurate preview no matter what I do.

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