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Digital Font Formats and Font Managment

Digital Font Formats and Font Managment

This presentation focuses on TrueType (TT), PostScript® Type 1 (T1), and OpenType® (OT) being the major multi-platform outline font data standards for print, a bit of history of font formats, and their file management in computer operating systems. “Outline font” means that they describe letter shapes — glyphs — by means of [control] points, which in turn define lines and Bézier curves. An outline font must be represented physically by the dots of the output device, whether it’s screen pixels or the dots of a laser, ink-jet or wire-pin printer. The process of converting outlines to a pattern of dots on the grid of the device is called “rasterization.”

The content was originally written un 2005, and published in Graphicus 1015, at the time the leading Italian magazine for the graphic industry, and consequently designed as a lecture (https://vimeo.com/464552790), a 2006 presentation on digital typography at IUAV Venice, Italy (http://www.iuav.it/). The slides were then updated in 2011 for teaching purposes. The OpenType variable technology should be part of the next update, together with grammatography.

Alessandro Segalini

March 30, 2006
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  1. © 2006–2011 Alessandro Segalini
    "#$%&'()*+,-./0123456789:;ŠŽ
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    ȗ Ș ș Ț Ȝ ȝ ȟ
    Digital Font
    Formats
    & Their Management

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  2. © 2006–2011 Alessandro Segalini
    Indeed,
    etymologically,
    font is female,
    from French “fonté,”
    “melting” – hence
    la font, la police, &c.
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •

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  3. © 2006–2011 Alessandro Segalini
    Types are:
    1. the parts of the font
    2. executive drawings
    &/or design drawings
    —in short “characters”
    are drawn or inked,
    “fonts” are licensed and used
    (i.e. sold, hence ethics, &c.).
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •

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  4. © 2006–2011 Alessandro Segalini
    The most relevant Byte data {ı Byte = 8 Bit, binary digits}
    of a font are the outlines.
    C
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •

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  5. © 2006–2011 Alessandro Segalini
    Contours (outlines) are of two kinds: white or black.
    A contour is a closed path.
    Directed contour
    Filled interior zone
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •
    Control Point
    Bézier Curve
    End Point
    End Point
    Smooth connection
    Sharp connection
    Control Vector

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  6. © 2006–2011 Alessandro Segalini
    The Metric data of a glyph are Cartesian information (x-y).
    .pfm
    .afm
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •
    Character width
    y
    x
    Right margin
    Baseline
    Origin point
    Right sidebearing
    Left sidebearing
    Adobe Font Metrics,
    ascii text-based
    font format.
    For Windows systems
    a .pfm file carries the
    metrics.

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  7. © 2006–2011 Alessandro Segalini
    The coordinates of every object in a font are represented
    by a standard measurement system:
    Usually, the height of a roman upper case is 7oo units.
    The height of the font is used as a value/parameter when
    scaling the types in the desired sizes.
    The font-unit is equal
    to ı/ıooo of the height
    of the body of the font,
    i.e., the ‘eM’ square.
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •
    -250
    Å
    712
    961
    y
    500
    System of coordinates for characters
    fontbureau.com/blog/the-em

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  8. © 2006–2011 Alessandro Segalini
    All the structural
    strokes in a
    character (glyph)
    are declared by
    Hint instructions:
    a pair of
    horizontal &
    vertical lines,
    plus the width
    of the Hint.
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •
    HVertical strokes (stem)
    Horizontal stroke (bar)
    Original outline
    Scaled without hinting Scaled with hinting
    Scaled outline Hint
    Hinting, more accurately called instructing, is a method
    of specifying how digital fonts display at small sizes on
    low-resolution devices, usually for on-screen usage.
    This is accomplished by providing instructions in
    the font file that define which pixels are turned on when
    producing bitmap images.

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  9. © 2006–2011 Alessandro Segalini
    ı2 x ı2 40 x 40
    200 x 200 2048 x 2048
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •

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  10. © 2006–2011 Alessandro Segalini
    PostScript (ps)
    page description language (pdl)
    (1976) 1985 – John Warnock
    —Computer display, low resolution, from 50 to 2ı6 pixels;
    —Dot-matrix printers, from ı00 to 250 dots per inch;
    —Ink-jet and Laser printers, from 300 to ı400 dpi;
    —Photographic technologies, 2400 dpi and above.
    1. Device-independent description: high-level imaging model.
    2. Raster output device software (interpret /render)
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •

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  11. © 2006–2011 Alessandro Segalini
    Bitmap

    mm
    tt
    ot
    Webfont
    PostScript
    Multiple Master
    TrueType
    OpenType
    .otf —.ttf
    Dot-matrix – one file, one body (size).
    3°grade Bézier, PostScript interpreter.
    Interpolation – weight, width, style, body.
    Internal rasterizer, Hinting potential.
    Unicode, ı6 Bit (65,ooo glyphs), +platform.
    Delivering on the fly; saved as a compressed
    container, supports licensing information,
    referenced within css by the @font-face rule.
    1976
    1984
    1990
    1991
    1996
    2009
    .bmp
    .pfb
    .mmf
    .ttf
    .otf —.ttf
    .woff
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •

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  12. © 2006–2011 Alessandro Segalini
    Bitmap

    mm
    tt
    ot
    woff
    PostScript
    Multiple Master
    TrueType
    tt, ps/cff
    Embeddable
    Xerox On-screen visualization of printing types
    Adobe (atm, Apple Laser Writer, PageMaker, dtp)
    Adobe T1 +, weight/width/optical-size/style axes, &c.
    Apple & Microsoft Standard, laser, no film-units.
    Apple & Microsoft Multilingual, only one font file.
    WebFonts Working Group www.w3.org/Fonts/WG
    1976
    1984
    1990
    1991
    1996
    2009
    .bmp
    .pfb
    .mmf
    .ttf
    .ttf – .otf
    .woff
    scaling intelligence supported at operating system level :
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •

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  13. © 2006–2011 Alessandro Segalini
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •
    M\Zkfi Flkc`e\
    9`kdXgg\[ M\Zkfi Flkc`e\
    9`kdXgg\[
    Impossible to convert from TT to T1 without accuracy loss.
    Uppercase Roman ‘O’ drawn by PostScript T1 splines…
    T1 = 3°grade Bézier curves
    and by TrueType curves.
    TT = subset, 2°grade equations

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  14. © 2006–2011 Alessandro Segalini
    PostScript uses “dumb” fonts and a “smart” interpreter.
    TrueType uses relatively smarter fonts and a dumber interpreter.
    Most of the high-res output devices use PostScript as page description
    language; PostScript fonts can be sent directly to those devices.
    PostScript hints tell the rasterizer what features ought to be controlled,
    and the rasterizer interprets these using its own “intelligence.”
    TrueType fonts are downloaded as bitmap or they require the rasterizer
    to be downloaded as a PostScript program, with a consequent slow
    down of the printing process. TrueType puts very specific instructions
    into the font to control how it will appear.
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •

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  15. © 2006–2011 Alessandro Segalini
    Unicode
    multi-bit character encoding
    WGL Character Set
    Unicode Shape Glyph name Unicode Name Unicode Block
    Awww.ascendercorp.com | ©2005 Ascender Corporation Page 4 of 19
    00A3 £ sterling pound sign Latin-1 Supplement
    00A4 ¤ currency currency sign Latin-1 Supplement
    00A5 ¥ yen yen sign Latin-1 Supplement
    00A6 ¦ brokenbar broken bar Latin-1 Supplement
    00A7 § section section sign Latin-1 Supplement
    00A8 ¨ dieresis diaeresis Latin-1 Supplement
    00A9 © copyright copyright sign Latin-1 Supplement
    00AA ª ordfeminine feminine ordinal indicator Latin-1 Supplement
    00AB « guillemotleft left-pointing double angle quotation mark Latin-1 Supplement
    00AC ¬ logicalnot not sign Latin-1 Supplement
    00AD uni00AD soft hyphen Latin-1 Supplement
    00AE ® registered registered sign Latin-1 Supplement
    00AF ¯ macron macron Latin-1 Supplement
    00B0 ° degree degree sign Latin-1 Supplement
    00B1 ± plusminus plus-minus sign Latin-1 Supplement
    00B2 ² uni00B2 superscript two Latin-1 Supplement
    00B3 ³ uni00B3 superscript three Latin-1 Supplement
    00B4 ´ acute acute accent Latin-1 Supplement
    00B5 µ mu micro sign Latin-1 Supplement
    00B6 ¶ paragraph pilcrow sign Latin-1 Supplement
    00B7 · periodcentered middle dot Latin-1 Supplement
    00B8 ¸ cedilla cedilla Latin-1 Supplement
    00B9 ¹ uni00B9 superscript one Latin-1 Supplement
    00BA º ordmasculine masculine ordinal indicator Latin-1 Supplement
    00BB » guillemotright right-pointing double angle quotation mark Latin-1 Supplement
    00BC ¼ onequarter vulgar fraction one quarter Latin-1 Supplement
    00BD ½ onehalf vulgar fraction one half Latin-1 Supplement
    00BE ¾ threequarters vulgar fraction three quarters Latin-1 Supplement
    00BF ¿ questiondown inverted question mark Latin-1 Supplement
    00C0 À Agrave latin capital letter a with grave Latin-1 Supplement
    00C1 Á Aacute latin capital letter a with acute Latin-1 Supplement
    00C2 Â Acircumflex latin capital letter a with circumflex Latin-1 Supplement
    00C3 Ã Atilde latin capital letter a with tilde Latin-1 Supplement
    00C4 Ä Adieresis latin capital letter a with diaeresis Latin-1 Supplement
    00C5 Å Aring latin capital letter a with ring above Latin-1 Supplement
    Unicode consists of a repertoire
    of more than ıo9,ooo characters
    covering 93 scripts; a set of code
    charts for visual reference, an
    encoding methodology and set of
    standard character encodings, an
    enumeration of character properties.
    One number, one character—language,
    application and platform independent.
    unicode.org
    decodeunicode.org
    diacritics.typo.cz
    wikipedia.org/unicode
    ascendercorp.com/wgl.html
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •
    Revision 6.0, 2011

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  16. © 2006–2011 Alessandro Segalini
    OpenType is a cross platform format for scalable computer fonts
    originally built on its predecessor TrueType, retaining the 8-bit
    TrueType’s basic structure and adding many intricate data
    structures for prescribing typographic behaviors that enhance
    the font’s typographic and language support capabilities.
    The extended support via Unicode allows OpenType fonts
    to have up to 65,536 glyphs and cover all languages and scripts
    admitted.
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •
    OpenType
    16-bit cross platform font format

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  17. © 2006–2011 Alessandro Segalini
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •
    /FontInfo
    /FontName
    /Encoding
    /PaintType
    /FontType
    /FontMatrix
    /FontBBox
    /UniqueID
    /Metrics
    /StrokeWidth
    /Private
    /CharStrings
    (/FID)
    dictionary
    name
    arra
    intege
    intege
    arra
    arra
    intege
    dictionary
    number
    dictionary
    dictionary
    fontID
    /version
    /Notice
    /FullName
    /FamilyName
    /Weight
    /ItalicAngle
    /isFixedPitch
    /UnderlinePosition
    /UnderlineThickness
    string
    string
    string
    string
    string
    number
    boolea
    number
    number
    /RD
    /ND
    /NP
    /Subrs
    /OtherSubrs
    /UniqueID
    /BlueValues
    /OtherBlues
    /FamilyBlues
    /FamilyOtherBlues
    /BlueScale
    /BlueShift
    /BlueFuzz
    /StdHW
    /StdVW
    /StemSnapH
    /StemSnapV
    /ForceBold
    /LanguageGroup
    /password
    /lenIV
    /MinFeature
    /RndStemUp
    procedur
    procedur
    procedur
    arra
    arra
    intege
    arra
    arra
    arra
    arra
    number
    intege
    intege
    arra
    arra
    arra
    arra
    boolea
    intege
    intege
    intege
    arra
    boolea
    /A
    /B
    /.notdef
    charstring
    charstring
    charstring
    .
    .
    .
    .
    .
    .
    /CharStrings dictionary
    /FontInfo dictionary /Private dictionary
    font dictionary
    Typical dictionary of the structure of a PostScript font program:

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  18. © 2006–2011 Alessandro Segalini
    Ergonis PopChar — mac, pc
    Lemke FontBook — mac
    Neuber Typograf — pc
    AMP Font Viewer — pc
    Wordmark.it — online
    Insider FontAgent — mac
    Linotype FontExplorerX — mac, pc
    Extensis Suitcase — mac, pc
    Proxima FontExpert — pc
    High-Logic MainType — pc
    FontLab, Fontographer — mac, pc
    FontForge — mac, pc, linux
    Glyphs — mac
    Fontstruct — online
    ergonis.com
    lemkesoft.de
    neuber.com
    ampsoft.net
    wordmark.it
    fontagent.com
    fontexplorerx.com
    extensis.com
    proximasoftware.com
    high-logic.com
    fontlab.com
    fontforge.net
    glyphsapp.com
    fontstruct.com
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •
    Font
    Browsers
    Font
    Managers
    Font
    Editors

    View full-size slide

  19. © 2006–2011 Alessandro Segalini
    Low Quality means:
    Incomplete set of characters.
    Inconsistency in the weight of the stems.
    Irregular and/or improper outline construction.
    An excess of points to describe a glyph.
    Unsuitable and/or inaccurate hinting.
    Inconsistently designed metric.
    Poor, excessive, or inexistent kerning.
    Other editing/legibility factors.
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •
    1.
    2.
    3.
    4.
    5.
    6.
    7.
    8.

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  20. © 2006–2011 Alessandro Segalini
    the essential elements of style have more to do with the
    goals typographers set for themselves than with the mutable
    eccentricity of their tools. ¶ In other words, typography itself
    is far more device-independent than PostScript – the computer
    language used to render these particular constructed letters,
    and the design of these pages, into typographic code.
    Writing systems vary, but a good page is not hard to learn to
    recognize, whether it comes from Táng Dynasty China, the
    Egyptian New Kingdom or Renaissance Italy. Typography is
    the craft of establishing human language with a durable form.
    High Quality means that…
    Digital Font Formats & Their Management
    • • • • • • • • • • • • • • • • • • • • •

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  21. © 2006–2011 Alessandro Segalini
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    Article
    Graphicus № ıoı5
    March 2005
    Digital Font Formats & Their Management
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  22. © 2006–2011 Alessandro Segalini
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