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Q: Sub pixel chromatic anti aliasing ( Answered 5 out of 5 stars,   0 Comments )
Subject: Sub pixel chromatic anti aliasing
Category: Computers > Graphics
Asked by: majidanwar-ga
List Price: $200.00
Posted: 28 Apr 2006 08:07 PDT
Expires: 28 May 2006 08:07 PDT
Question ID: 723683
A question about chromatic anti-aliasing and Microsoft Cleartype: it
seems that there are a number of vendors who use the same basic
technique of sub-pixel anti-aliasing using the individual colour
components of an LCD to increase the apparent resolution of typefaces.
MS Cleartype is the most widely known, but the Mac XOS Panther and
Adobe CoolType apparently use this technique. According to MS patent
6,188,385 claim 1 the method of improving resolution of the displayed
image comprising pixel sub-components each of a different color. In
otherwords, the entire concept of chromatic anti-aliasing appears to
have been claimed by Microsoft, nevertheless, this seems to be a
widely used technique as used by others above. How is it possible that
Adobe and Apple can use this technique without infringing Microsoft
patents ?
Subsequent question: is the simple technique described on to reduce colour fringing (basically
convolute the sub-pixel values to spread the results horizontally)
also patented by Microsoft, Adobe, or others or are they widely known
techniques that are free to use by all ?
Subject: Re: Sub pixel chromatic anti aliasing
Answered By: leapinglizard-ga on 30 Apr 2006 15:21 PDT
Rated:5 out of 5 stars
Dear majidanwar,

I was attracted to your question because of my professional interest in
intellectual-property disputes, which includes my involvement last year
in patent litigation at a major corporation.

It is not obvious that Microsoft owns a valid patent on the subpixel
rendering technology embodied in its ClearType software. The validity of
the Microsoft patents related to this software has been disputed ever
since the introduction of ClearType in 1998. A New York Times article
from that year describes some of the informal counterclaims.

    But within hours of the introduction, the Internet was buzzing
    with claims that Cleartype was suspiciously similar to approaches
    developed many years earlier by researchers at Apple Computer,
    IBM, Xerox Corp. and elsewhere.


    "They may have found a minor twist," Brown said, "but the idea
    of how the eye perceives color based on the display of sub-pixels
    is where we started this game."


    Other industry researchers acknowledge that the Cleartype
    technology will make screens sharper, but insist that the
    underlying concepts have been known for decades.


    The most direct challenge to Microsoft's claim of originality,
    however, comes from Dpix Inc., a Xerox subsidiary spun off from
    the Palo Alto Research Center. Dpix makes a high-resolution,
    7 million-pixel color flat-panel display using techniques that
    seem to closely parallel Cleartype technology.

    In the Dpix display each pixel is composed of four sub-pixels --
    two green and two red-and-blue -- to increase the readability
    of the fonts above and beyond the resolution of the screen,
    which is already twice that of today's standard flat panels.


    Microsoft's application for patent protection for its
    font technology is one reason the announcement has stirred
    controversy. Software was not routinely patented until the
    mid-to-late 1980s, so the Patent Office does not have a rich
    database on which to draw when assessing software claims.

New York Times: Microsoft's Cleartype Sets Off Debate on Originality

As the article points out, the practice of patenting software is a
relatively recent one, making it difficult for the U.S. Patent Office
to make sound judgments as to what software patents are legitimate. The
chief difficulty with U.S. patents in general is that the Patent Office
does not have enough staff or guaranteed funding to adequately handle
the volume of applications filed every year.

These shortcomings of the American patent system were spectacularly
illustrated by the recent BlackBerry case, in which a patent holder
managed to extort hundreds of millions of dollars from Research In
Motion (RIM), the independent inventor and developer of the BlackBerry
technology. The patent holder was able to tie up RIM for years in court
and to threaten its entire customer base with a court-mandated service
suspension, even though the U.S. Patent Office belatedly found that the
patents at stake were actually invalid.

    Understaffing at the United States Patent and Trademark Office
    -- there are thirty-four hundred examiners and three hundred
    and fifty thousand applications a year -- means that patent
    examiners don?t have enough time to properly research an
    idea?s originality. And since the office is funded by patent
    fees, as opposed to getting its budget from Washington, it
    has a financial incentive to process applications as quickly,
    rather than as diligently, as possible. (Generally, examiners
    spend somewhere between eleven and twenty-two hours per patent,
    and no extra time is allocated for commercially significant
    applications.) The appellate court responsible for patent cases
    also tends to be patent-holder-friendly. Injunctions of the
    kind that N.T.P. got against R.I.M., for instance, are usually
    employed only to prevent ?irreparable harm,? but in patent
    cases they are now routine.


    Since 1980, the number of applications has tripled, and the
    number of patents granted has nearly quadrupled, effectively
    allowing patent holders to rope off more and more of the economy,
    even though the quality of patents has been steadily declining. (A
    recent Federal Trade Commission report warned that ?questionable
    patents are a significant competitive concern and can harm
    innovation.?) The BlackBerry mess is a case in point: in the
    past year, the Patent Office has reŽxamined N.T.P.?s eight
    patents, and issued preliminary rulings declaring them, and the
    nineteen hundred claims they contain, invalid. Until those patents
    are formally invalidated, however, R.I.M. is still on the hook,
    so it may end up paying for infringements that it never committed.

The New Yorker: James Surowiecki: BlackBerry Picking

The RIM case demonstrates that a patent is only valuable to the extent
that the patent holder is willing and able to defend it. If Adobe and
Apple persist in employing their own subpixel rendering technologies
despite the ClearType patents, it is because they feel that Microsoft
would not be able to enforce the patents against them. They must
be confident that either (a) their own technologies are sufficiently
different from ClearType that there is no infringement, or (b) that the
Microsoft patents would be readily invalidated by a finding of prior art.

However, it is not necessarily the case that Apple is ignoring the
ClearType patents altogether. In the first place, noted Microsoft
evangelist Robert Scoble has declared in a web forum that there is
a licensing agreement between Microsoft and Apple concerning certain
aspects of subpixel rendering.

    Bill Hill told me separately that Apple actually does license
    at least some of the rendering technology in ClearType.

Microsoft Developer Network: Channel 9: Cleartype Team - Typography in
Windows Vista

Second, the method used by Apple is different from that of Microsoft,
perhaps sufficiently so that Apple feels it has no need to fully license
ClearType, as Agfa Monotype has done.

    Apple has started using subpixel rendering in recent versions
    of Mac OS X. Version 10.2 introduced subpixel rendering of
    type and Quartz vector graphics. This feature is enabled using
    the System Preferences panel "General" (10.2) or "Appearance"
    (10.3), by setting the font smoothing style to "Medium ?
    best for Flat Panel". The quality of the rendering compared
    to Microsoft's ClearType is contested. Some consider Quartz to
    produce higher-quality output, while most prefer the ClearType
    style. Generally, ClearType is richer in contrast but cannot
    be fine-tuned by the user, since the anti-aliasing property
    is embedded in each font. Mac OS X allows the user to select
    the largest point size that font smoothing will be applied
    to. However, text produced by Mac OS X's font smoothing produces
    visible artifacts for almost all fonts at any point size.
Wikipedia: Apple typography: Subpixel rendering
    ClearType manipulates the intensity of such sub-pixels in effect
    to roughly triple the available resolution of a display. Quartz
    and Adobe Acrobat both do something similar, but with lesser
    results at smaller font sizes (at least on my PowerBook).
    So why did Apple implement a "halo" anti-aliasing model (when
    ClearType and Adobe's Acrobat text anti-aliasing seem more
    exacting)? The answer may lie in patents over the technology. If
    Apple cannot obtain a license on Microsoft's low resolution
    (i.e., small font size) sub-pixel rendering techniques, then we
    may simply have to wait until April 10, 2020 (when Microsoft's
    patent runs out).
    Legally illegible?

    Apple may actually possess a license to this technology as part
    of Microsoft's US$150 million investment back in 1997. However,
    it's uncertain that their patent portfolio cross-licensing
    agreement encompasses technology made after 1997. If Apple has a
    free license to this technology, then it should certainly use it;
    not employing the Microsoft, sub-pixel, rastering techniques at
    (least at) smaller sizes in Quartz might boil down to hubris.

MacObserver: John Kheit: MS's ClearType KOs Apple's Quartz In The
Lightweight Division

Even the Adobe system, which is much closer to ClearType than Apple is,
uses a different method to calculate the luminance of the subpixels
adjoining the whole pixels in a displayed image.

    Revolutionary? Well, maybe not, because whatever you may have
    heard, this technology is not new, having been bandied about
    for so long ?- almost 25 years -- it's debatable whether the
    underlying concepts are even patentable any longer. [...]

    The technique in question is called color anti-aliasing, and
    both Adobe and Microsoft go about it in pretty much the same
    way, albeit with different algorithms to iron out the wrinkles,
    so to speak.


    The ultimate trick of ClearType and CoolType is to apply an
    algorithm (likely the patentable part for each vendor) that uses
    the colors of adjoining pixels to eliminate the unwanted color
    cast created in the non-black portion of the split pixel. This
    "pixel-borrowing" technique is just one of those being tested.

Seybold Reports: James Felici: ClearType, CoolType: The Eyes Have It

You point out that Claim 1 of U.S. Patent 6,188,385 is a broad description
of subpixel rendering. The claim is so broad, in fact, that Microsoft
would have a great deal of trouble defending it against the argument
that it is invalidated by prior art.

The notion of adjusting pixel sub-components independently of a
whole pixel was used in many earlier inventions, among them a light
pen developed by Steve Gibson, the author of the "Free & Clear Demo"
you cite yourself. In fact, Steve Gibson has argued that his own work
is predated by that of Steve Wozniak, the Apple co-founder, who used
subpixel rendering to enhance the resolution of the Apple II monitor.

    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.


    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.

Gibson Research Corporation: Sub-Pixel Font Rendering Technology: Who
Did It First?

Because the specific technology used in Gibson's Free & Clear Demo was
implemented by him decades earlier, he does not infringe in any way on
Microsoft's later patent. If anyone is in the wrong, it is Microsoft for
taking out a patent on the much earlier idea. Given the extensive history
of subpixel rendering technology, it is no surprise that Microsoft has
initiated no litigation against Gibson, Apple, or Adobe.

    Technologist Steve Gibson, a software developer and consultant
    whose claim to fame was inventing the light pen more than a
    decade ago, says he recognizes 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.


    Microsoft representatives professed unfamiliarity with the
    Apple technique.


    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.
PC World: ClearType Draws from Apple II, Says Developer

There is nothing unusual about this situation, since a great number
of patents are later found to be invalid due to the existence of prior
art that was unknown to the patent office or to those applying for the
patent. This does not prevent some unscrupulous patent holders, however,
from exploiting weaknesses in the legal system to enforce bad patents
before they can be invalidated, which is exactly what happened in the
BlackBerry case. The proliferation of bad patents is one of several
reasons why there has been a recent movement against the introduction
of software-patent legislation in the European Union, where software
patents have not been formally recognized so far.
    Whereas software patents are unfortunately legal in the U.S.,
    they still have very questionable validity in Europe. Though
    they're not legally enforceable, over 30,000 patents on software
    have been granted. [...]

    The idea of selling products over the Internet has already been
    patented in the U.S., and Amazon used its "one-click buying"
    patent to famously sue Barnes & Noble in the late 1990s.
    Examples of currently granted European Patents are EP803105
    and EP738446. These patent the idea of selling objects over a
    network using a server, client, and payment processor, or using
    a client and a server. In other words, these are patents on
    selling products over the Internet; clearly a lot of software
    would infringe on these overzealous patents.

O'Reilly Network: Software Patents in the EU

To recapitulate, the fact that Microsoft has been granted patents
for ClearType does not mean that ClearType is a new idea, nor does it
guarantee that the patents can be enforced. The fact that Microsoft 
has not chosen so far to enforce them suggests that it recognizes their
weakness. As for Gibson's Free & Clear demonstration, anyone is entitled
to use the specific technology used therein, which was invented and
applied many years ago. The question of whether the earlier subpixel
rendering technologies at Apple, Xerox, and elsewhere constitute prior
art against ClearType, thereby making the Microsoft patents invalid,
is a question the courts would decide if it ever came to litigation.

I have enjoyed answering your question. If you have any concerns about
the completeness or accuracy of my research, please advise me through
a Clarification Request and allow me the opportunity to fully meet your
needs before you rate this answer.



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majidanwar-ga rated this answer:5 out of 5 stars
Excellent answer - structured, fair, balanced and detailed. Also
directly answered the question and committed a knowledgeable opinion,
rather than avoid or fudge the issue with a "sit-on-the-fence"

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