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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.

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Alessandro Segalini

March 30, 2006
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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 • • • • • • • • • • • • • • • • • • • • •
  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 • • • • • • • • • • • • • • • • • • • • •
  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 • • • • • • • • • • • • • • • • • • • • •
  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
  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.
  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
  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.
  9. © 2006–2011 Alessandro Segalini ı2 x ı2 40 x 40

    200 x 200 2048 x 2048 Digital Font Formats & Their Management • • • • • • • • • • • • • • • • • • • • •
  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 • • • • • • • • • • • • • • • • • • • • •
  11. © 2006–2011 Alessandro Segalini Bitmap tı 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 • • • • • • • • • • • • • • • • • • • • •
  12. © 2006–2011 Alessandro Segalini Bitmap tı 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 • • • • • • • • • • • • • • • • • • • • •
  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
  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 • • • • • • • • • • • • • • • • • • • • •
  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
  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
  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:
  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
  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.
  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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  22. © 2006–2011 Alessandro Segalini • • • • • •

    • • • • • • • • • • • • • • •