RE: Free Fonts

From: Philippe Verdy (verdy_p@wanadoo.fr)
Date: Wed Dec 03 2003 - 21:20:03 EST

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    Kenneth Whistler writes:
    > Patent #1: US5155805: Method and apparatus for moving control points
    > in displaying digital typeface on raster output devices. May 8, 1989.
    >
    > Patent #2: US5159668: Method and apparatus for manipulating outlines
    > in improving digital typeface on raster output devices. May 8, 1989.
    >
    > Patent #3: US5325479: Method and apparatus for moving control points
    > in displaying digital typeface on raster output devices. May 28, 1992.
    >
    > "It's important to understand that the patents do not prevent
    > anyone from reading, converting or generating TrueType fonts.
    > As they only concern the subtle art of hinting TrueType glyphs,
    > it's even possible to legally display text with TrueType fonts,
    > as long as the patented techniques aren't used to optimise the
    > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    > bitmaps at small pixel sizes."
    > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    >
    > The abstract for US5155805 starts out: "A method for manipulating
    > the control points of a symbol image represented by an outline
    > font to improve the appearance of the font on raster output devices
    > ^^^^^^^^^^^^^^^^^^^^^^^^
    > which are under control of a computer."
    > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    > There, is that clear enough for you?

    It seems clear to me that this looks like a call by Apple to font authors to
    offer high quality fonts to their clients, but clients cannot use them to
    render text with these hinted fonts without getting a licence for the
    renderer they need.

    As FreeType does not offer to its users such a license, it cannot implement
    hinting mechanisms in its renderer. So FreeType cannot use fonts hinted with
    Apple technology. This means that font authors cannot seriously sell hinted
    font designs to FreeType users, and these fonts will only work in compliant
    environment that include such a license such as Windows, MacOSX, and
    possibly other vendor-supported environemnts.

    May be it's possible in Linux with a commercial distribution like RedHat, if
    RedHat pays its license distribution rights to Apple, but then FreeType
    would need to be modified to include that licensed material and this may
    expose it to license problems if FreeType uses the GPL which requires
    contributing the modified source code to anyone asking them. That's what is
    known as the "viral" nature of the GPL.

    If FreeType uses the GPL, it will have to include a generic extension
    mechanism to support a commercial extension of a compliant hinting renderer,
    so that commercial vendors like RedHat can provide the needed licensed
    renderer within their distribution.

    Another way would be to develop another hinting system that does not include
    something claimed in the above patents. It will be hard even if the technics
    and formats used are completely different, because the terms of the patent
    are quite vague and seem to cover nearly all the aspects of font hinting,
    which is exactly a way to move control points that define glyphs.

    The only alternative seems to be hinting fonts with something else than
    moving control points; for example by embedding bitmaps of glyphs at small
    sizes, so that no control points are involved in this operation, or by
    providing alternate sets of glyphs, but this breaks the continuity of the
    font at any intermediate size, even if antiscaling is used to limit this
    effect.

    If the patent was only in the supported table formats and instructions
    defined in Apple's specification, then other formats could be used and
    provided within font designs and used within compliant renderers that only
    use these alternate hinting tables. But will typographers accept to develop
    these alternate font tables when more than 99% of their market uses a
    Microsoft of Apple OS or a propriatary Unix system, or a commercial Linux
    distribution?

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