ClearType draws from Apple II, says developer

The ClearType technology that Microsoft heralded at Comdex as a revolutionary way to sharpen screen text may actually be more than 20 years old and an Apple Computer invention. Technologist Steve Gibson says he recognises the technique as one used in the Apple II. Microsoft has declined to release technical specifications or white papers explaining ClearType in detail, citing its pending patents - but if Gibson is right it may already be in the public domain.

The ClearType technology that Microsoft heralded at Comdex as a revolutionary way to sharpen screen text may actually be more than 20 years old and an Apple Computer invention.

Technologist Steve Gibson, a software developer and consultant whose claim to fame was inventing the light pen more than a decade ago, says he recognises the technique as one used in the Apple II. He confirmed his suspicion by comparing notes with Apple cofounder Steve Wozniak, who developed a font-smoothing technique for the Apple II. Gibson suggests that Microsoft tidies on-screen text displays by essentially splitting pixels, and then recombining the pixels so images are sharper, smoother and easier to read.

In his Comdex keynote speech, Microsoft CEO Bill Gates emphasised that ClearType would be useful technology in hand-held and flat-panel displays.

Microsoft representatives professed unfamiliarity with the Apple technique. They described ClearType as a breakthrough that builds on Microsoft's TrueType technology and uses the same rasterizer (the software that generates fonts).

Microsoft has declined to release technical specifications or white papers explaining ClearType in detail, citing its pending patents.

But Gibson says the technology may be in the public domain. He says the pixel-splitting and sharing technique was patented and used by Apple when the Apple II was released in 1976. The Apple II patents were released into the public domain when the patents expired 17 years later.

"Microsoft has rediscovered something that was old," says Gibson, who is president of Gibson Research in Laguna Hills, California. "My chagrin is seeing all the hype -- they're talking about this like it's the second coming."

His hope is that Microsoft will indeed use the technology in Windows and other products, but that other developers -- including Apple and makers of Unix operating systems -- will also be free to implement the technique without having to pay royalties to Microsoft.

In fact, Gibson is working on a freeware program that will demonstrate the Apple technique so other developers can program software to produce ClearType-like results.

Gibson said something seemed familiar when he watched Gates' Comdex keynote on the Web. He dug around in his garage until he found some old Apple II manuals and schematics that described the technique of borrowing part of an adjacent pixel to create a cleaner image.

"If you wanted to make some image more nicely formed, you'd borrow a subpixel from the adjacent pixel, to make one pixel half a pixel wider," Gibson says. "That's exactly what Microsoft is doing with ClearType." Because Gates says ClearType improves image resolution 300 percent, Gibson suspects Microsoft is splitting pixels into thirds: red, green, and blue for the primary colors used in color monitors. The Apple II monitors were monochrome.

What's more, Gibson found a reference in a manual for Microsoft BASIC for the Apple II product that referenced pixel orientation in a way that shows how pixels can be shared.

Gibson's essay on the subject is at http://grc.com/cleartype.htm

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