On 11/01/2011 11:07 PM, Yang Li wrote:

? 2011/11/2 10:46, Sergiu Dumitriu ??:

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Hey community,

I spent some time trying to make PDF export work for CJK (Chinese, Japanese, Korean) characters, and managed to get it working quite well.

Searching for some good open source fonts, I finally decided on the following:

- CJK Unifonts (Linux re-packaging of the Arphic fonts) - IPAGothic - Baekmuk

The first one comes in two variants, serif (a.k.a. ming or song) and script (regular script, kai), and has good support for Chinese, with good, but not complete, support for Japanese, and no support for Korean. It looks very good in both variants, but we should decide on one of them. I uploaded samples on http://jira.xwiki.org/browse/XWIKI-7106 to see how they would look.

*** Q1: Should Kai or Ming be used as the default export font for Chinese? ***

I'm far from being an expert here, but my opinion is that the Kai variant, with it's handwritten look, is better suited for printed material. Still, PDFs are also used on screen, be that a large computer monitor or a handheld device, and on screen the legibility of the Ming variant is better. One option that I like is to use Kai for normal text and Ming for tt/code elements, as a kind of monospace.

As a Chinese, I strongly recommend *song* , the most poluar font, and we seldom use ming in official documents...

Reading on Wikipedia http://en.wikipedia.org/wiki/Ming_%28typefaces%29 I got the impression that there isn't a clear distinction between Ming and Song, and some refer to the same thing with both terms. Looking at the list of CJK fonts http://en.wikipedia.org/wiki/List_of_CJK_fonts none of the fonts that have Song in their name are under an open source friendly license, so they can't be redistributed. Please take a look at the sample PDF and see if it is acceptably similar to Song: http://jira.xwiki.org/secure/attachment/23886/ming-over-freefont.pdf

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The second font, IPAGothic, is centered on Japanese, so it has good support for Japanese, some support for Chinese, and no support for Korean. It is a sans-serif variant.

The third font, Baekmuk, brings support for Korean (laking from the other two fonts), along with little support for some Chinese and Japanese characters. This one comes in more variants, but only two are complete enough to be considered, Batang as the serif equivalent, and Gulim as the sans-serif equivalent.

*** Q2: Should Batang or Gulim be used for Korean? ***

My opinion is that the serif variant looks better on print, although less readable. Still, I've seen Gulim much more often used in practice. I attached two samples for this as well to the Jira issue.

*** Q3: Should the current FreeSerif font be used for non-CJK characters, or the font face defined in the font specific to each language? ***

While I prefer FreeSerif for all English text, I've seen in practice that the preferred solution is to use a bulkier font for numbers and latin characters. FreeSerif is good.

OK, noted.

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*** Q4: Does italics/oblique make sense for CJK characters? ***

The concept of Italics is defined only for latin-like characters, and no font provides support for italics CJK. Still, Firefox does render slanted characters for CJK text inside <em>. FOP, the rendering engine used for generating PDFs, does not have support for automatically slanting fonts that don't provide an italics variant, and will insist on choosing a font that comes in an italics variant. So, this means that by default any text that is emphasized in the wiki will not be displayed in the PDF correctly (they would appear as # characters). There is a simple solution, and that is to alter the font file so that is says that both the regular and italic version of the font are in the file. Another option is to actually provide an oblique version of the font, which FontForge seems to be able to do quickly and with good results. Still, this will double the size of the fonts, so I'd rather not provide italic fonts if they don't actually make much sense for native CJK users.

In fact, Chinese people use bold font to emphasize (hei), not italics, and we seldom use italics.

OK, so this means that italics doesn't make sense, which is good. The bad news is that FOP doesn't support making characters bold when there's no predefined font, either, but it won't fall back to a font that does provide bold. This means that bold text will appear the same way as regular CJK. I tried to generate a bold font from FontForge, but it fails with an error message: "some fragments did not join". So, our hope is that FOP will implement this feature soon.

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Some other fonts that I looked at were: * the Droid font used in Android devices, which is a sans-serif font IMO not suited for print; its advantage would be that it provides a unitary look for all CJK languages, less good looking, but more legible * the Hanazono font, which has impressive support for all the characters in CJK Unicode sets, but was created in a wiki way, so IMO it's not very consistent throughout the whole spectrum, and not as esthetically looking as the others

*** Q5: Should a less good looking, but smaller and more consistent font be used? If yes, which one? ***

The Droid font is actually quite small compared to the others, and on smaller font sizes it is more readable.

I prefer normal fonts, because nowadays we usually use a browser and large display @@..

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I would really appreciate some feedback on this topic.

-- Sergiu Dumitriu http://purl.org/net/sergiu/