Re: Arabic letters separated by markup

From: John Hudson (
Date: Mon Jun 13 2005 - 17:57:34 CDT

  • Next message: Mete Kural: "Re: Arabic letters separated by markup"

    Chris Jacobs wrote:

    > So the photofont would have a red arab alphabet with a red lam, a black arab
    > alphabet with a black aleph, and built-in ligaturing so if you give the
    > glyph numbers for red lam black aleph you get the red-black lam-aleph glyph
    > instead?
    > What is the problem with the coloration controls then? They come before the
    > ligaturing and have to encode just one color in each glyph number they
    > yield.
    > unicode lam in red context passes thru coloration control procedure yields
    > red lam glyph number
    > unicode aleph in black context passes thru coloration control procedure
    > yields black aleph glyph number
    > and then red lam black aleph passes thru ligaturing yields multicolor glyph.
    > Should work.

    Not in any current software. This is all feasible, but really on the fringes of both text
    layout and font technology. Photofonts are funky, but outside of some Photoshop plugins
    are not supported; they are currently a graphics development format, not a final display
    format for live text. Also, this approach would only be viable so long as your user didn't
    want yellow and pink, or purple and orange, or some other colour combination that your
    photofont doesn't support.

    Colouration controls in applications are based on colouring individual glyphs in common
    outline format fonts such as TrueType. Colouring is just about the last thing that happens
    to a glyph after text has been laid out, which is one of the reasons why, excepting the
    case of ligatures, it is trivial. There is no interraction at all between font glyph
    shaping and colouration.

    As I say, it is possible to invent perfectly feasible means to deal with this issue, but I
    really don't see it as being high on anyone's list of priorities.

    I've spent a lot of time thinking about bi-colour text in the context of Ethiopian
    punctuation marks, which are traditionally black and red. The glyph references in the
    Unicode charts show the black portion of these marks, which are acceptable in themselves,
    but the traditional rendering is almost always augmented with additional red dots.

    John Hudson

    Tiro Typeworks
    Vancouver, BC
    Currently reading:
    Truth and tolerance, by Benedict XVI, Cardinal Ratzinger as was
    War (revised edition), by Gwynne Dyer

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