Microsoft ClearType reinvents the anti-aliased text wheel

Been there, seen it, done it, bought T-shirt, says Adobe

Microsoft has invented system-wide anti-aliased text -- again. Adobe was the first company to invent anti-aliased text, back in the mid-80s when it released the first version of Display PostScript. It invented it once more with Adobe Type Manager (ATM), often harshly dubbed Adobe Type Mangler by users. In the early 90s, Acorn added system-wide anti-aliased fonts. Apparently. Microsoft is the latest claimant to the anti-aliasing invention crown with ClearType, demoed during Bill Gates' Comdex keynote. According to Dick Brass, Microsoft's VP of technology development, quoted by InfoWorld, ClearType allows fonts to be displayed at up to 300 per cent of the resolution of the imaging device. "We are able to address the area in between the pixels," said Brass. "You are no longer bound by the number of pixels on the screen." His second sentence makes rather more sense than the first. Since the pixel is the smallest screen element on any display, it's clearly not possible to address the space between them. What you can do, however, is render text in memory as, say, a 150 dots per inch (dpi) bitmap and then display that bitmap in the screen space in which you'd normally render text at the default resolution of the device, say 72dpi or lower if it's an LCD screen. This is essentially what applications like Photoshop do when showing hi-res graphics on a 72dpi monitor. The image appears smaller, but that's OK provided you take into account the shrinkage when you render the original text. Provided you can display at least 256 levels of grey, the image will look fine. All easy stuff, in fact, and not quite the breakthrough Gates and co. are praising the technology as. Whether this is Microsoft's method will remain to be seen, but its likely to be a variation of it. Brass suggested that ClearType adds functionality to Windows' TrueType rasteriser, and you would need to work with non-bitmap fonts (as TrueType does) to make this approach to anti-aliased text work. ®

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