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Who Did It First?

The Distant Origins of Sub-Pixel Font Rendering

Microsoft's November 1998 Comdex announcement of it's "breakthrough" new display technology, dubbed 'ClearType' was regarded by many as the most important event of the show.

I COMPLETELY AGREE that incorporating this technology into Microsoft's Windows operating environments will be an absolute win for its LCD display panel users. But Microsoft was apparently unaware that twenty-two years ago Apple II programmers were using these techniques — rooted in Apple technology patents — to improve the effective resolution of their video displays.

Moreover, as we will see below, many other well known companies including IBM, Xerox PARC, and Honeywell have since spent a great deal of time exploring and optimizing the application of sub-pixel imaging techniques.

These facts will be significant to Microsoft, and to the industry at large, because software techniques developed and widely employed for many years cannot be the proper subject of contemporary intellectual property protection. These techniques are owned by the public and may be freely used today by, and for, the benefit of everyone.

So while I agree with Microsoft that this is indeed "breakthrough technology", it is in fact very old "breakthrough technology" that has always been owned by the public. I'm quite excited that something Steve Wozniak may have first invented so many years ago has returned in a form that will be able to benefit all users of personal computing platforms, whether they're running Windows, Mac OS, Unix, Linux, or other portable color LCD-based displays.

But let's back up a bit before
we get ahead of ourselves ...

During his Comdex Keynote speech, Microsoft's chairman and CEO, Bill Gates, referred to a new LCD-oriented font display technology dubbed (and trademarked) 'Microsoft ClearType'. He claimed up to 300 percent display resolution increase and dramatically enhanced display clarity and readability.

If your system is equipped with Microsoft's Media Player you can view Bill's Comdex keynote from this link.  His discussion of the 'ClearType' technology begins at roughly 19 minutes into the stream.

You can get an accurate and unbiased sense for Microsoft's position on ClearType from the beginning of their ClearType press release:

LAS VEGAS -- Nov. 15, 1998 -- Tonight at COMDEX/Fall '98, Bill Gates, chairman and CEO of Microsoft Corp., unveiled an unprecedented innovation in font display technology during his keynote address. The software, called Microsoft® ClearType(tm) font technology, dramatically improves font display resolution and marks a genuine breakthrough in screen readability.

ClearType improves display resolution by as much as 300 percent and works especially well on existing LCD devices, including desktop flat panels, laptops and smaller devices such as Handheld and Palm-size PCs. By profoundly improving the on-screen reading experience, ClearType font technology enables new product categories such as electronic books (eBooks), while benefiting the display of existing spreadsheets, word processing documents and Internet content.

Gates hailed ClearType as a leap forward in screen sharpness during his COMDEX keynote address. Assisted by typography expert and Microsoft researcher Bill Hill, Gates demonstrated the technology to thousands of people. To provide an intimate view of the new software, Microsoft also will show the software on desktop and laptop PCs at its COMDEX booth, L#2202.

"We have overcome a major obstacle to ubiquitous on-screen reading -- bad readability," said Nathan Myhrvold, Microsoft chief technology officer. "The astounding results we have achieved with this software innovation give us a level of readability that wasn't expected for perhaps another five years. And it works without new hardware on existing displays."


Click Here for the entire ClearType Press Release.

Personal Computing History: Revisited or Revisionist?

I can well understand Microsoft's excitement over their apparently independent rediscovery of these techniques, but we should not lose sight of the fact that this is very well explored technological territory.

Microsoft must have forgotten that twenty-two years ago the famous Apple II personal computer employed and patented exactly this sort of solution for its high-resolution graphics display. Their sub-pixel addressing was used to double the effective horizontal resolution of the Apple II video display.

The Apple II's highest resolution mode was 280 pixels horizontally by 192 vertically. However, this was really the 'sub-pixel' resolution. (Similar to the example above where an 800 pixel wide LCD is really 2400 sub-pixels wide.) The Apple II's display generated two sub-pixels per pixel. On an LCD display every third sub-pixel is Red, Green, or Blue and all three must be turned on to get white. On the Apple II, every other sub-pixel was green or purple and they both needed to be turned on in order to get white.

If sub-pixel technology had not been in common use on the Apple II, a diagonal white line could only have been drawn using 'whole' white pixels composed of paired green and purple sub-pixels. (As shown here.)
But thanks to Apple's built-in sub-pixel technology, white pixels were often composed from each half of adjacent whole pixels to yield a much smoother result.

As we saw above, this is exactly what today's sub-pixel rendering technology achieves with modern-day LCD panels.

We know that Microsoft understood this back then, since page 170 of their own "Microsoft BASIC Interpreter Reference Manual", copyright 1980, states:

Note that because of the way in which home TV's work, a high resolution dot plotted with HCOLOR=3 (white) or HCOLOR=7 (white) will be white only if both (x,y) and (x+1,y) are plotted. If only (x,y) is plotted, the dot will be blue when x is even and green when x is odd.
Click here to see the actual page.

Microsoft made a typo in their manual, since they meant 'purple' rather than 'blue'. But they are clearly saying that adjacent sub-pixels must be turned on in order to get white, otherwise a color will result. This is exactly the case for LCD panels where white pixels are composed of all three (R-G-B) sub-pixels. The Apple II utilized two (Green/Purple) sub-pixels as shown above.

Click to Enlarge
( Click to Enlarge )   
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I was an active developer of Apple II graphics hardware and software at the time, having created the best-selling LPS II high-resolution high-performance light pen system for Apple II computers. (Known in the industry as the 'Gibson Light Pen' and later renamed to that after Koala licensed the product.) As a result of that involvement I well recall that the idea of combining adjacent non-white sub-pixels to increase the effective resolution of the Apple II's video was commonplace and freely discussed. It was also well documented in books, trade publications, and even Microsoft's own manuals of the era.

Furthermore, many software examples can be found where developers were 'borrowing' adjacent sub-pixels in order to tune the width of an Apple character font or other graphics feature. For example, all of my software did this.

Given this information, it is my sincere hope that Microsoft will acknowledge that they, in fact, rediscovered old and well-proven technology, and that they will not attempt to acquire and/or enforce overly broad patents which would certainly be overturned following a closer examination of PC industry history. This technology is too important for any one company — especially a company that didn't invent it — to attempt to prevent its free use within the industry. I hope Microsoft will understand this.

What does Steve Wozniak have to say about this?

I had a conversation about this with an old friend of mine who is in a position to know: In reference to Microsoft's ClearType technology announcement, Woz (Steve Wozniak, the designer of the Apple II and inventor of its patented technologies) said, and gave me explicit permission to post this quote:

"Back in 1976, my design of the Apple II's high resolution graphics system utilized a characteristic of the NTSC color video signal (called the 'color subcarrier') that creates a left to right horizontal distribution of available colors. By coincidence, this is exactly analogous to the R-G-B distribution of colored sub-pixels used by modern LCD display panels. So more than twenty years ago, Apple II graphics programmers were using this 'sub-pixel' technology to effectively increase the horizontal resolution of their Apple II displays."

Hmmmmm. So, although the Apple II and LCD display panels obviously utilize very different technologies, they share a coincidental common nature which allows these old and well worn sub-pixel graphics programming techniques to be re-used with today's modern LCD panels! Isn't that very cool!?

So Who Did This First?

Given the array of players who have occupied and explored this territory through the years, it would be difficult to say who was here first. Sure, if we needed to reconstruct history we certainly could. But enough has already been learned, revealed and documented for any doubt to be quenched that this sub-pixel font rendering technology was long ago established and is based upon technology that's soundly located in the public's hands. And this is as it should be, since the popularity and falling prices of active matrix LCD panels, coupled with the well-known benefits of sub-pixel graphics rendering, promise to soon revolutionize the readability of LCD displayed text.

Thus, Microsoft's 'ClearType' application of sub-pixel text rendering does not represent the dramatic breakthrough that they claim and it can not be the valid subject for intellectual property acquisition. Nevertheless, I'm excited to have them participating in this field, and I eagerly anticipate the day when our desktop LCD, laptop, and color PDA display screens will be empowered with sub-pixel text rendering technology created through the research efforts of all these fine participants.

You may continue your exploration of this
fascinating topic with any of the links below:

How Sub-Pixel Font
Rendering Works
Turning Theory
into Practice
The Free & Clear
Rendering Demo
The True Origins
of these Ideas
Q & A
Other Resources
on the Web
Sub-Pixel Rendering Home PageSteve's Page

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Last Edit: May 25, 2005 at 15:18 (7,000.58 days ago)Viewed 5 times per day

ClearType is a trademark of Microsoft Corporation, Redmond, WA