====== Embed TrueType fonts in PDF ======

TrueType and the newer variant OpenType fonts are ubiquitous on current computers. It is therefore desirable to use these fonts in PDFs. Most of these fonts have a liberal enough licence to allow embedding.

This text is for developers who implement PDF. Embedding imvolves creating two objects: /Font and /FontDescriptor. While /Font is document dependent defining the encoding and widths, the /FontDescription is only dependent on the information from the font itself. This page aims to summerize the information about how to gather the correct information from a TrueType font, which is distributed among several specifications.

Disclaimer: I develop on Windows and, therefore, I don't have experience nor knowledge about Mac or Linux environments.
===== The /Font object =====

see PDF spec (2.0: 9.6.2.1, 1.7: 9.6.1) "Type 1 fonts - General"
and PDF spec (9.6.3) "TrueType fonts"

<code><< 
  /Type           /Font
  /Subtype        /TrueType
  /BaseFont       <Name>
  /FirstChar      <Integer>
  /LastChar       <Integer>
  /Widths         <array of Integer>
  /Encoding       <an encoding>
  /ToUnicode      <a CMap>
  /FontDescriptor <a FontDescriptor>
>></code>

==== /BaseFont ====

The /BaseFont name is the PostScript name in the "name" table of the font:
<code>name -> ID 6</code>

The PostScript name is special, since it never contains blanks.

The spec states: <code>In the absence of a PostScript language name in the "name" table, a PostScript language name should be derived from the name by which the font is known in the host operating system.</code>

No further information is given... I am looking into all installed TrueType/OpenType fonts on my Windows 10 computer.
Of the 526 fonts, 313 have the right identifier (first 4 bytes): ''(/000/001/000/000)''.
All 313 fonts have a name table with a PostScript name, so that the fallback does not need to be used. Because of this lack of test cases, I leave a ''#halt'' in the code for this case - maybe some day such font will come by.

The only hint on how to find the right OS name on Windows is an undocumented gdi32 function: [[https://stackoverflow.com/questions/42135461/c-powershell-undocumeted-winapi-function-getfontresourceinfow]].


==== /Encoding ====

/Encoding is /WinAnsi or a dict (see PDF spec ...) Don't know yet

==== /Widths, /FirstChar and /LastChar ====

/Widths lists all the widths of the glyphs of the current encoding starting with code /FirstChar up to /LastChar.

==== /ToUnicode ====

For accessebility add /ToUnicode with a CMap mapping from the code to unicode.

===== The /FontDescriptor object =====

The required attributes for embedding are:

<code>
<<
  /Type /FontDescriptor
  /FontName    <Name>     "same as /Font/BaseName"
  /Flags       <Integer>
  /FontBBox    <Array with 4 numbers>
  /ItalicAngle <Number>
  /Ascent      <Number>
  /Descent     <Number>
  /CapHeight   <Number>   "not for symbolic fonts"
  /StemV       <Number>
  /FontFile2   <Stream>                           "for TrueType"
  /FontFile3   <Stream with /Subtype /OpenType>   "for OpenType"
>></code>

==== /Flags ====


=== Bit 1: FixedPitch ===

From table 'post' #isFixedPitch see [[https://learn.microsoft.com/en-us/typography/opentype/spec/post]]

=== Bit 2: Serif ===

=== Bit 3: Symbolic ===

True, if there are any characters in the font which are not in the Standard Latin character set (PDF Spec D.2).

=== Bit 4: Script ===

=== Bit 6: Nonsymbolic ===

Must be the inverse of Bit 3 (Symbolic)

=== Bit 7: Italic ===

=== Bit 17: AllCap ===

=== Bit 18: SmallCap ===

=== Bit 19: ForceBold ===


==== /FontBBox ====


==== /ItalicAngle ====


==== /Ascent ====


==== /Descent ====


==== /CapHeight ====


==== /StemV ====


==== /FontFile(2|3) ====