Adobe CIDs and glyphs in CJK TrueType font

Adobe CIDs and glyphs in CJK TrueType font (aka CJKTTCID.INF in gs-cjk project)

## Table of contents

> - Overview
> - Notes of CJKTTCID
> - Future Works
> - References

For other information, see the Ghostscript overview.

## Overview

This note provides information on utilization of CJK (Chinese, Japanese and Korean) TrueType fonts as Type 2 CID-keyed fonts from the viewpoint of its validity and limitation. In order to compose Type 2 CID-keyed font from CJK TrueType font on the fly, gs-cjk project uses not only general-purpose (ToCID) CMaps but also ToUnicode and ToCode CMaps which are freely distributed with Acrobat Reader by Adobe Systems Incorporated. The current algorithm of mapping CIDs to TTF completely depends on Adobe CMaps, TrueType cmap and GSUB tables.

The current revision of on-the-fly Type 2 CID-keyed font technology supports the following kinds (RO: Registry-Ordering) of CID-keyed fonts: ``

    	[RO]
    	Adobe-CNS1
    	Adobe-GB1
    	Adobe-Japan1
    	Adobe-Japan2
    	Adobe-Korea1

and doesn't support the following kinds of CID-keyed fonts:
`

    	[RO]
    	Adobe-CNS2
    	Adobe-HongKong1
    	Adobe-Korea2
    	Adobe-Vietnam1

`
The current revision can handle the following kinds (Encoding in cmap table) of TrueType fonts as CID-keyed fonts:
`

    	[Encoding]	[RO]
    	Unicode		Adobe-*
    	ShiftJIS	Adobe-Japan1
    	PRC		Adobe-GB1
    	Big5		Adobe-CNS1
    	Wansung		Adobe-Korea1
    	Johab		Adobe-Korea1

`
and doesn't support UCS-4 Encoding TrueType fonts for the present. In the case of Unicode Encoding, RO can be detected by reading ``Code Page Character Range'' of OS/2 table of TTF as follows:
`

    	[Encoding]	[Code Page]		[RO]
    	Unicode		Japanese		Adobe-Japan1
    			Simplified Chinese	Adobe-GB1
    			Korean Wansung		Adobe-Korea1
    			Traditional Chinese	Adobe-CNS1
    			Korean Johab		Adobe-Korea1

`
For each combination of RO and TTF Encoding, following Adobe CMaps are applied:
`

    	[RO-Encoding]		[Supplement limit]
    		[used CMap]		- [Comment]

    	Adobe-CNS1-Big5		0
    		Adobe-CNS1-ETen-B5	- ToCode CMap
    		ETen-B5-V		- ToCID CMap
    		ETen-B5-H		- ToCID CMap

    	Adobe-CNS1-Unicode	3
    		Adobe-CNS1-UCS2		- ToUnicode CMap
    		UniCNS-UCS2-V		- ToCID CMap
    		UniCNS-UCS2-H		- ToCID CMap

    	Adobe-GB1-PRC		2
    		Adobe-GB1-GBK-EUC	- ToCode CMap
    		GBK-EUC-V		- ToCID CMap
    		GBK-EUC-H		- ToCID CMap

    	Adobe-GB1-Unicode	4
    		Adobe-GB1-UCS2		- ToUnicode CMap
    		UniGB-UCS2-V		- ToCID CMap
    		UniGB-UCS2-H		- ToCID CMap

    	Adobe-Japan1-ShiftJIS	2
    		Adobe-Japan1-90ms-RKSJ	- ToCode CMap
    		90ms-RKSJ-V		- ToCID CMap
    		90ms-RKSJ-H		- ToCID CMap

    	Adobe-Japan1-Unicode	4
    		Adobe-Japan1-UCS2	- ToUnicode CMap
    		UniJIS-UCS2-V		- ToCID CMap
    		UniJIS-UCS2-H		- ToCID CMap

    	Adobe-Japan2-Unicode	0
    		UniHojo-UCS2-V		- ToCID CMap
    		UniHojo-UCS2-H		- ToCID CMap

    	Adobe-Korea1-Johab	1
    		KSC-Johab-V		- ToCID CMap
    		KSC-Johab-H		- ToCID CMap

    	Adobe-Korea1-Unicode	2
    		Adobe-Korea1-UCS2	- ToUnicode CMap
    		UniKS-UCS2-V		- ToCID CMap
    		UniKS-UCS2-H		- ToCID CMap

    	Adobe-Korea1-Wansung	1
    		Adobe-Korea1-KSCms-UHC	- ToCode CMap
    		KSCms-UHC-V		- ToCID CMap
    		KSCms-UHC-H		- ToCID CMap

`
where Supplement values are denoted as the limit determined by the maximum CID in used CMaps.

The Glyph Substitution table (GSUB) of TTF, Single Substitution Format 2 is read for vertically-used glyphs in CIDs. The current revision doesn't handle any other formats of GSUB, so handling ligatures and variants as CID-keyed fonts might be tasks to be solved in future.

In recent CID-keyed fonts, pre-rotated Latin glyphs are defined, but the current revision merely maps to normal Latin glyphs. I don't know whether gs-cjk project can handle pre-rotated glyphs or not in future.

## Notes of CJKTTCID

In the following tables and comments, I note details of validity and limitation for the individual kinds of CID-keyed fonts composed from generally-circulated and Unicode TrueType fonts at the current revision. Naturally, these results of glyphs lacking are affected by TrueType fonts you use.
``

    Adobe-CNS1 CID-keyed font composed from Traditional Chinese Unicode TTF
    -----------------------------------------------------------------------
    [ROS]		[CID range]	[Comment]
    Adobe-CNS1-0	    0-  505	96,97,124-127,228,260 are lacking
    		  506-  561	no problem
    		  562-  594	all glyphs are lacking
    		  595-13645	no problem
    		13646-13748	13646,13647 are lacking
    		13749-13998	13996-13998 are lacking
    		13999-14098	some glyphs are lacking
    Adobe-CNS1-1	14099-17407	lots of glyphs are lacking (*1)
    Adobe-CNS1-2	17408-17600	17503,17504 are lacking (*2)
    Adobe-CNS1-3	17601-17605	17603 is lacking
    		17606-18845	lots of glyphs are lacking (*3)
    Adobe-CNS1-4	18846-18961	all glyphs assignment is impossible (*4)
    (*1) HK GCCS
    (*2) not pre-rotated
    (*3) HK SCS
    (*4) HK SCS (unused in UniCNS-UCS-2 CMap, though used in UniCNS-UTF8,
    UniCNS-UTF16, UniCNS-UTF32, also ETHK-B5, needless to say HKscs-B5)

    Adobe-GB1 CID-keyed font composed from Simplified Chinese Unicode TTF
    ---------------------------------------------------------------------
    [ROS]		[CID range]	[Comment]
    Adobe-GB1-0	    0-  939	99,695,698,737,935,938 are lacking
    		  940- 7702	no problem
    		 7703- 7716	7705,7708 are incorrect
    Adobe-GB1-1	 7717- 9896	no problem
    Adobe-GB1-2	 9897-22126	no problem
    Adobe-GB1-3	22127-22352	22347,22350,22352 are lacking (*1)
    Adobe-GB1-4	22353-22427	all glyphs are not available (*2)
    		22428-29058	all glyphs are not available (*3)
    		29059-29063	all glyphs are not available (*4)
    (*1) not pre-rotated
    (*2) additional Hiragana and Katakana, extended Bopomofo glyphs
    (*3) the Unified Han Ideographs Extension A
    (*4) pre-rotated glyphs

    Adobe-Japan1 CID-keyed font composed from Japanese Unicode TTF
    --------------------------------------------------------------
    [ROS]		[CID range]	[Comment]
    Adobe-Japan1-0	    0- 1124	lots of glyphs are lacking or incorrect:
    				96-98,127,128,130-133,135-137,226,326,
    				390,396,422,424,502,506-509,512,513,515,
    				606,607,632
    		 1125- 7477	no problem
    		 7478- 7632	7478 is lacking and 7608,7609 are incorrect
    		 7633- 8004	lots of glyphs are lacking or incorrect (*4)
    		 8005- 8283	lots of glyphs are lacking or incorrect:
    				8008,8053,8059-8061,8091,8102-8111,8166-8181,
    				8189,8190,8227-8229,8260
    Adobe-Japan1-1	 8284- 8358	lots of glyphs are lacking or incorrect:
    				8295-8297,8300-8302,
    				8306,8307,8321,8322,8325,8326
    Adobe-Japan1-2	 8359- 8717	no problem
    		 8718- 8719	8718 is lacking and 8719 is incorrect
    Adobe-Japan1-3	 8720- 9353	some glyphs are lacking or incorrect (*1)
    Adobe-Japan1-4	 9354- 9737	some glyphs are lacking or incorrect (*2)
    		 9738-13319 	lots of glyphs are lacking or incorrect (*3)
    		13320-15443	all glyphs are variants or lacking (*4)
    (*1) not pre-rotated
    (*2) not italic form
    (*3) many ligature, pre-rotated, pre-rotated and italic form glyphs
    (*4) lots of variants are assigned substitutes

    Adobe-Japan2 CID-keyed font composed from Japanese Unicode TTF
    --------------------------------------------------------------
    [ROS]		[CID range]	[Comment]
    Adobe-Japan2-0	    0- 6067	no problem

    Adobe-Korea1 CID-keyed font composed from Korean Unicode TTF
    ------------------------------------------------------------
    [ROS]		[CID range]	[Comment]
    Adobe-Korea1-0	    0-  357	some glyphs are lacking or incorrect:
    				61,97,100,104,111,227
    		  358- 3435	no problem
    		 3436- 8055	no problem
    		 8056- 8190	lots of glyphs are lacking or incorrect:
    				8059,8061,8075,8083-8085,8089,8091,8093,8190
    		 8191- 9332	no problem
    Adobe-Korea1-1	 9333-18154	perhaps no problem, but I can't check (*)
    Adobe-Korea1-2	18155-18351	some glyphs are lacking
    (*) Technical Note on Adobe-Korea1-1,2 has not been published yet[6].

## Future Works

As stated above, I think that the current mapping algorithm based on ToCID CMaps and ToUnicode CMaps still has problems. The gs-cjk project is considering how to settle the matters.

## References

1. Microsoft Corporation, ``OpenType specification,'' http://www.asia.microsoft.com/typography/otspec/
2. Adobe Systems Incorporated, ``Adobe-CNS1-4 Character Collection for CID-Keyed Fonts,'' http://partners.adobe.com/asn/developer/pdfs/tn/5080.Adobe-CNS1-4.pdf
3. Adobe Systems Incorporated, ``Adobe-GB1-4 Character Collection for CID-Keyed Fonts,'' http://partners.adobe.com/asn/developer/pdfs/tn/5079.Adobe-GB1-4.pdf
4. Adobe Systems Incorporated, ``Adobe-Japan1-4 Character Collection for CID-Keyed Fonts,'' http://partners.adobe.com/asn/developer/pdfs/tn/5078.Adobe-Japan1-4.pdf
5. Adobe Systems Incorporated, ``Adobe-Japan2-0 Character Collection for CID-Keyed Fonts,'' http://partners.adobe.com/asn/developer/pdfs/tn/5097.Adobe-Japan2-0.pdf
6. Adobe Systems Incorporated, ``Adobe-Korea1-0 Character Collection for CID-Keyed Fonts,'' http://partners.adobe.com/asn/developer/pdfs/tn/5093.Adobe-Korea1-0.pdf
7. Taiji Yamada, ``Tips on PostScript,'' http://www.aihara.co.jp/~taiji/tops/
8. ``gs-cjk project,'' http://www.gyve.org/gs-cjk/

This article is written by Taiji Yamada <taiji@aihara.co.jp>. He takes full responsibility for the wording and content of this article.

Copyright © 2001 Taiji Yamada <taiji@aihara.co.jp> and gs-cjk project.

Copyright © 2002 artofcode LLC. All rights reserved.

This file is part of GNU Ghostscript. See the GNU General Public License (the "License") for full details of the terms of using, copying, modifying, and redistributing GNU Ghostscript.

GNU Ghostscript version 6.53, 13 February 2002