CHAPTER 5
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Text
5.9.2 ToUnicode CMaps
The CMap defined in the
ToUnicode
entry of the font dictionary must follow the
syntax for CMaps introduced in Section 5.6.4, “CMaps” and fully documented in
Adobe Technical Note #5014,
Adobe CMap and CIDFont Files Specification.
Addi-
tional guidance regarding the CMap defined in this entry is provided in Adobe
Technical Note #5411,
ToUnicode Mapping File Tutorial.
This CMap differs from
an ordinary one in the following ways:
•
The only pertinent entry in the CMap stream dictionary (see Table 5.17 on
UseCMap
, which may be used if the CMap is based on another
ToUnicode
CMap.
•
The CMap file must contain
begincodespacerange
and
endcodespacerange
operators that are consistent with the encoding that the font uses. In particular,
for a simple font, the codespace must be one byte long.
•
It must use the
beginbfchar
,
endbfchar
,
beginbfrange
, and
endbfrange
opera-
tors to define the mapping from character codes to Unicode character sequenc-
es expressed in UTF-16BE encoding.
Identity−H
CMap to map from
character codes to CIDs and whose descendant CIDFont uses the
Identity
map-
ping from CIDs to TrueType glyph indices. Text strings shown using this font
simply use a 2-byte glyph index for each glyph. In the absence of a
ToUnicode
en-
try, no information would be available about what the glyphs mean.
Example 5.15
14 0 obj
<< /Type /Font
/Subtype /Type0
/BaseFont /Ryumin−Light
/Encoding /Identity−H
/DescendantFonts [ 15 0 R ]
/ToUnicode 16 0 R
>>
endobj
15 0 obj
<< /Type /Font
/Subtype /CIDFontType2
/BaseFont /Ryumin−Light