For those who are not aware, there are twelve IDCs (Ideographic Description Characters) in Unicode, from U+2FF0 through U+2FFB, that are used in IDSes (Ideographic Description Sequences) which are intended to visually describe the structure of ideographs by enumerating their components and arrangement in a hierarchical fashion. Any Unicode character can serve as a IDS component, and the IDCs describe their arrangement. The IRG uses IDSes as a way to detect potentially duplicate characters in new submissions. All existing CJK Unified Ideographs have an IDS, and new submissions require an IDS.
This article describes a technique that uses IDSes combined with OpenType functionality to pseudo-encode glyphs that are unencoded or not yet encoded. If memory serves, it was Taichi KAWABATA (川幡太一) who originally suggested this technique.
I was recently asked, indirectly via Twitter, about changes and additions that were made to our JIS2004-savvy CMap resources, specifically UniJIS2004-UTF32-H and UniJISX02132004-UTF32-H. The former also includes UTF-8 (UniJIS2004-UTF8-H) and UTF-16 (UniJIS2004-UTF16-H) versions that are kept in sync with the master UTF-32 version by being automagically generated by the CMap resource compiler (and decompiler), cmap-tool.pl, which I developed years ago.
Of course, all of these CMap resources also have vertical versions that use a “V” at the end of their names in lieu of the “H,” but in the context of OpenType font development, the vertical CMap resources are virtually unused and worthless because it is considered much better practice to explicitly define a ‘vert‘ GSUB feature for handling vertical substitution. In the absence of an explicit definition, the AFDKO makeotf tool will synthesize a ‘vert’ GSUB feature by using the corresponding vertical CMap resources.
With all that being said, what follows in this article is a complete history of these two CMap resources, which also assign dates, and sometimes notes, to each version.
As described in last month’s article, our tools engineer developed two Python scripts for assembling and disassembling ‘sfnt’ collections, both of which operate on TrueType-based source fonts to produce a traditional TrueType Collection (TTC) font or to break apart one, but also operate on CFF-based source fonts to produce a new font species known as an OpenType Collection (OTC).
The purpose of this follow up article is to convey the news that these scripts have been tweaked slightly, and have been included in a new version of AFDKO that was released on 2014-02-18 as Build 61250. One of the benefits of the integration with AFDKO is that the tools are now easier to run, as a simple command.
I would like to use this opportunity to introduce two new things.
First, OpenType Collections. TrueType Collections have been around for many years, and are commonplace for OS-bundled fonts. What I am speaking of are ‘sfnt’ Collections that include a ‘CFF ‘ (PostScript charstrings) table rather than a ‘glyf‘ (TrueType charstrings) one. The advantage of an ‘sfnt’ Collection is that fonts that differ in minor ways can be combined into a single resource, which can provide substantial size savings.
Second, brand new AFDKO tools, in the form of two Python scripts, for building, breaking apart, and displaying a synopsis of an OTC’s tables. These scripts were developed by our incredibly talented font tools engineer, Read Roberts, so all thanks should go to him for preparing them.
I spent a couple of days curling up with GB 18030 (both versions: 2000 and 2005), which is PRC’s latest and greatest national character set standard, and came across an oddity that my gut tells me is a design flaw. At the very least, it is an issue about which font developers need to be aware.
What I found were eight instances of CJK Unified Ideographs with a left-side Radical #130 that uses the Traditional Chinese or Taiwan-style form, instead of the expected Simplified Chinese or PRC-style form that looks the same as Radical #74. Screen captures from the latest Unicode Code Charts, whose glyphs agree with both versions of GB 18030, are shown below:
As I described in Part 1, Part 2, and Part 3 of this series, Standardized Variants offer a Normalization-proof representation for the 1,002 CJK Compatibility Ideographs, which are encoded in the BMP, and at the end of Plane 2. These 1,002 Standardized Variants have been approved, and will be included in Unicode Version 6.3. They will, of course, also be included in IS0/IEC 10646.
In an effort to provide to font developers advance support for the Standardized Variants that correspond to glyphs in Adobe’s public ROSes, the next version of AFDKO will include a new version of the Adobe-Japan1_sequences.txt file that appends entries that correspond to 89 of these Standardized Variants, along with Adobe-CNS1_sequences.txt and Adobe-Korea1_sequences.txt files that specify 14 and 270 entries, respectively, that correspond to these Standardized Variants. If you click on the file names, you can download the files and use them immediately. These are used with the AFDKO makeotf tool, and specified as the argument of the “-ci” command-line option.
In an effort to make sure that the infrastructure to support UTR #50 (Unicode Vertical Text Layout) will be in place—sooner rather than later—I spent a significant part of last week working with key people within Adobe, and at Microsoft and W3C, to put together a proposal for a new OpenType feature, to be tagged ‘vrtr’, for supporting this soon-to-be published standard. Below is full description that we came up with, and which was submitted for inclusion in the OpenType Specification and in OFF (ISO/IEC 14496-22 or Open Font Format):
Friendly name: Vertical Alternates For Rotation
Registered by: Adobe/Microsoft/W3C
Function: Transforms default glyphs into glyphs that are appropriate for sideways presentation in vertical writing mode. While the glyphs for most characters in East Asian writing systems remain upright when set in vertical writing mode, glyphs for other characters—such as those of other scripts or for particular Western-style punctuation—are expected to be presented sideways in vertical writing.
Example: As a first example, the glyphs for FULLWIDTH LESS-THAN SIGN (U+FF1C; “＜”) and FULLWIDTH GREATER-THAN SIGN (U+FF1E; “＞”) in a font with a non-square em-box are transformed into glyphs whose aspect ratio differs from the default glyphs, which are properly sized for sideways presentation in vertical writing mode. As a second example, the glyph for LEFT SQUARE BRACKET (U+005B, “[“) in a brush-script font that exhibits slightly rising horizontal strokes may use an obtuse angle for its upper-left corner when in horizontal writing mode, but an alternate glyph with an acute angle for that corner is supplied for vertical writing mode.
Recommended implementation: The font includes versions of the glyphs covered by this feature that, when rotated 90 degrees clockwise by the layout engine for sideways presentation in vertical writing, differ in some visual way from rotated versions of the default glyphs, such as by shifting or shape. The vrtr feature maps the default glyphs to the corresponding to-be-rotated glyphs (GSUB lookup type 1).
Application interface: For GIDs found in the vrtr coverage table, the layout engine passes GIDs to the feature, then gets back new GIDs.
UI suggestion: This feature should be active by default for sideways runs in vertical writing mode.
Script/language sensitivity: Applies to any script when set in vertical writing mode.
Feature interaction: The vrtr and vert features are intended to be used in conjunction: vrtr for glyphs intended to be presented sideways in vertical writing, and vert for glyphs to be presented upright. Since they must never be activated simultaneously for a given glyph, there should be no interaction between the two features. These features are intended for layout engines that graphically rotate glyphs for sideways runs in vertical writing mode, such as those conforming to UTR#50. (Layout engines that instead depend on the font to supply pre-rotated glyphs for all sideways glyphs should use the vrt2 feature in lieu of vrtr and vert.) Because vrt2 supplies pre-rotated glyphs, the vrtr feature should never be used with vrt2, but may be used in addition to any other feature.
UTC (Unicode Technical Committee) Meeting #136 took place last week, and one of the significant outcomes was that UTR (Unicode Technical Report) #50 was advanced from Draft to Approved status. Congratulations to Koji ISHII (石井宏治), its editor, and also to Eric Muller, who took the initiative to start this project and served as its first editor.
I have advocated the use of the special-purpose and language-neutral Adobe-Identity-0 ROS over the past few years, and have developed several CID-keyed fonts that take advantage of this ROS, but keep in mind that its use can act like a double-edge sword.
On one hand, it provides font developers with great flexibility, in terms of the glyph complement of a font. In other words, font developers need not be restricted to one of our public CJK ROSes, such as Adobe-Japan1-6, or a subset thereof. Kazuraki is an example of a Japanese font whose glyph set requirements didn’t fit Adobe-Japan1-6, so the Adobe-Identity-0 ROS was used.
On the other hand, font developers need to develop all of the necessary resources, such as the UTF-32 CMap Resource that is used as the basis of the ‘cmap‘ table, which maps Unicode code points to glyphs in the font, along with any GSUB features. In addition, and because the Adobe-Identity-0 ROS is language-neutral in that its designation does not specify or suggest a primary language, some applications may incorrectly assign a primary language to such fonts. This, of course, is due to heuristics (発見的教授法 in Japanese), or more specifically, their failure.
Unicode has become the de facto way in which to represent text in digital form, and for good reason: its character set covers the vast majority of the world’s scripts. Other benefits of Unicode include the following:
- That it is under active and continuous development, meaning that with each new version, more scripts are being supported, and additional characters for existing scripts are being standardized.
- That it is aligned and kept in sync with ISO/IEC 10646 (available at no charge), which is quite a feat.
With regard to font development, Unicode is considered the default encoding for OpenType, which refers to the ‘cmap‘ table. The most common ‘cmap’ subtables are Formats 4 (BMP-only UTF-16) and 12 (UTF-32). The latter is used only when mappings outside of the BMP (Basic Multilingual Plane), meaning from one or more of the 16 Supplementary Planes, are used.
[This Japanese version of the May 31, 2013 article entitled CSS Orientation Test OpenType Fonts is courtesy of Hitomi Kudo (工藤仁美).]
五月三十一日にアドビの新しいオープンソースプロジェクトで、「CSS Orientation Test OpenType Fonts」をリリースしたのでお知らせします。このオープンソースプロジェクトは、Unicodeの次期UTR #50（「Unicode Vertical Text Layout」）のエディタである石井宏治氏のリクエストをもとに開発された、二つのOpenType/CFFフォントを含みます。これらフォントの目的は、フォント開発者がより簡単にグリフの方向に関するテストを行えるよう考慮したものです。
I am pleased to announce that the new CSS Orientation Test OpenType Fonts open source project was launched on Adobe’s open-source portal, Open@Adobe, today. This open source project consists of two OpenType/CFF fonts that were developed at the request of Koji Ishii (石井宏治), the editor of Unicode’s forthcoming UTR #50 (Unicode Vertical Text Layout). The purpose of these fonts is for developers to be able to more easily test whether glyph orientation in their implementation is correct or not.
OpenType fonts are ‘sfnt’ (scalable font) resources that are comprised of several well-defined tables. One of these tables, which is the topic of today’s article, is the ‘cmap‘ (character map) table. The ‘cmap’ table, put simply, maps characters codes to Glyph IDs (GIDs) that refer to glyphs in the ‘glyf‘ or ‘CFF‘ (Compact Font Format) table, depending on the “flavor” of the OpenType font. What is important about the ‘cmap’ table is that it makes the glyphs usable. Without the ability to map from character codes, which are used by virtually all applications and OSes, the glyphs in a font are useless, and cannot be readily accessed or used.
The prototypical Serif and Sans Serif typeface style distinction in Korean has traditionally used the names Myeongjo (명조체/明朝體 myeongjoche) and Gothic (고딕체/고딕體 godikche), respectively. But, in 1993, the Republic of Korea (South Korea) Ministry of Culture, in an attempt to standardize typographic terms, recommended the use of Batang (바탕 batang) and Dotum (돋움 dotum) as the proper names for these two typeface styles.
At the time the Ministry of Culture recommendation was made, which was a period when printing was the most common use of fonts, Batang was meant for body text, and Dotum was for display or emphasis purposes. Mobile devices have provided a new use for Dotum, because its lack of serifs provided superior readability on mobile devices with smaller screens that necessitated smaller point sizes, and the original rationale for these new names seems to no longer apply.
From what I can tell, Korean type foundries have not embraced the Batang and Dotum names, and have actually resisted their use. What probably didn’t help was the fact that Microsoft released TrueType fonts with these exact names, with no additional qualifiers: Batang and Dotum. In other words, it seems that Microsoft’s use of these names polluted their chance at more widespread use, because they were treated as typeface names, not typeface style names.
In closing this brief article, I am curious about what our blog readership thinks about this particular issue. I welcome any and all comments.
As I wrote nearly a year ago, the Adobe-Identity-0 ROS is useful for building special-purpose fonts, especially CJK ones whose glyph coverage does not match one of our public ROSes. Our latest Adobe-Identity-0 ROS font is the open-source Adobe Blank, whose purposes and implementation details are described on our sister blog, Typblography.
I will close this particular topic by detailing how to support these proposed standardized variants in OpenType/CFF fonts.
For fonts that are currently IVS-enabled, such as those that include Format 14 ‘cmap’ subtables with Adobe-Japan1 or Hanyo-Denshi IVSes, it is important to note that the proposed standardized variants can co-exist with them, at least in terms of being specified in the font. For the former, I created an Adobe-Japan1_sequences.txt file that includes all registered Adobe-Japan1 IVSes, along with 89 of the 1,002 proposed standardized variants. The 89 standardized variants are at the end of the file. AFDKO tools, such as makeotf and spot, already support these standardized variants. When building OpenType/CFF fonts using the makeotf tool, this file is specified as the argument of the “-ci” command-line option.
To continue from the December 26, 2012 article, I should first point out that there is a relationship between these 1,002 proposed standardized variants and IVSes (Ideographic Variation Sequences). Standardized variants are standardized, hence their name. IVSes, on the other hand, are registered via a process that is described in UTS #37 and administered by the IVD Registrar (which happens to me at the moment).
One problem that has been plaguing CJK Compatibility Ideographs is the fact that they are adversely affected by normalization. Regardless of which of the four normalization forms is applied—NFC, NFD, NFKC, or NFKD—they are converted to their canonical equivalents, which are CJK Unified Ideographs. This is a problem, particularly for Japan, because 75 kanji in JIS X 0213:2004 kanji map to CJK Compatibility Ideograph code points. Furthermore, 57 of these 75 kanji correspond to Jinmei-yō Kanji (人名用漢字), meaning that they are used for personal names. The bottom-line problem with CJK Compatibility Ideographs is that any application of normalization, by any process, will permanently remove any distinctions between a CJK Compatibility Ideograph and its canonical equivalent. Not all processes are under one’s direct control, meaning that it is impossible to guarantee that normalization will not be applied. My opinion is that it is prudent to assume that normalization will be applied, and that preemption is the best solution.
In the December 4, 2012 Old Hangul article I mentioned that the ‘ccmp’ GSUB feature that is referenced in Microsoft’s Developing OpenType Fonts for Korean Hangul Script document is not necessary. Jaemin Chung kindly pointed out to me that environments that do not yet support Unicode Version 5.2 still require the ‘ccmp‘ (Glyph Composition/Decomposition) GSUB feature to be present, otherwise proper shaping will not happen.
The main purpose of this short article is to provide a revised Perl script, named mkoldhangul-ccmp.pl, that adds a complete ‘ccmp’ GSUB feature definition for environments that do not yet support Unicode Version 5.2 (or greater). The sample glyph-map.txt datafile that maps the Unicode-based glyph names to CIDs is unchanged.
Okay. It is time to put some “K” into CJK…
Seriously, much of the content of this blog has been focused on Chinese and Japanese issues. This article will provide some much-deserved Korean content.
I spent the last few days coming to grips with Old Hangul (옛한글 yethangeul), specifically how to implement proper shaping using the three registered OpenType GSUB features, ‘ljmo‘ (Leading Jamo Forms), ‘vjmo‘ (Vowel Jamo Forms), and ‘tjmo‘ (Trailing Jamo Forms).