Re: [m17n] Font rendering for Japanese

UTUMI Hirosi さんは書きました:

--- Mike FABIAN wrote:

...

The easiest way to disable embedded bitmaps for Japanese would be to remove the line

<string>ja</string>

in /etc/fonts/suse-pre-user.conf.

ok. (but does it disable hinting? Hinting is not good for CJK [or square] characters)

It worked quite well as long as Akito San's patch was included, the IPA fonts were rendered nicely as well. As this patch is gone now, I disabled the hinting for the IPA fonts. See this part in /etc/fonts/suse-pre-user.conf: <!-- Since we updated to freetype 2.1.10, the patch from http://www.kde.gr.jp/~akito/patch/freetype2/2.1.7 could not be applied anymore. Unfortunately the rendering quality of CJK fonts suffered a lot because of this update. The most extreme loss of rendering quality happened for the IPA fonts. See also http://bugzilla.novell.com/show_bug.cgi?id=105626 For other CJK fonts it is not that bad and on top of that most other CJK fonts have a wide range of embedded bitmaps which are used by default. And for big sizes, where there are not bitmaps anymore, the rendering quality is good anyway. As a workaround, switch of the hinting by setting hintstyle=hintnone for the IPA fonts: --> <match target="font"> <test name="family"> <string>IPAMincho</string> <string>IPAGothic</string> <string>IPAPMincho</string> <string>IPAPGothic</string> <string>IPAUIGothic</string> </test> <edit name="hintstyle"> <const>hintnone</const> </edit> </match> We could easily disable the hinting for all CJK fonts with something like this: <!-- Hinting for CJK fonts in freetype doesn't yet work as well as for Latin fonts. But our freetype package has the patch from http://www.kde.gr.jp/~akito/patch/freetype2/2.1.7 applied which improves the hinting results for CJK fonts a lot. If you are using a freetype package without that patch you may prefer to switch off hinting by setting hintstyle=hintnone for CJK fonts. This can be achieved by using the following rule: <match target="font"> <test name="lang" compare="contains"> <string>ja</string> <string>zh</string> <string>ko</string> </test> <edit name="hintstyle" mode="assign"> <const>hintnone</const> </edit> </match> --> which is also in /etc/fonts/suse-pre-user.conf but currently commented out because for the other CJK fonts the hinting appears to be not that bad as for the IPA fonts.

...

And I guess that a font designer who includes embedded bitmaps in his fonts does this because he believes they give better results than the outlines. If the font designer doesn't think so, why include embedded bitmaps at all?

MS Windows 9x can't show antialiased outlines, so MS fonts/IPA fonts include embedded bitmaps to show small characters clearly. But freetype2 shows outlines beautifully, so I think outlines are better than bitmaps.

Even on MS Windows XP, anti-aliasing is enabled by default only for sizes > 18 pixels. I didn't test the Japanese fonts but I verified that this is indeed the case for western fonts. To switch on anti-aliasing, the user has to select "Clear Type" in the Windows control centre manually. That means, the default look and feel of MS Windows XP looks rather bitmap like. These are not really bitmaps but outlines rendered without anti-aliasing with very high quality, which achieves practically the same quality as hand tuned bitmaps. Recently, during the beta phase of SuSE Linux 10.0, I made this the default for a selected list of fonts which have good byte code. See the following part of /etc/fonts/suse-pre-user.conf: <!-- ************************************************************ --> <!-- Hinting and antialiasing --> <!-- ************************************************************ --> <!-- Fonts which have high quality byte code interpreter instructions can look very good in small sizes when rendered in black and white (antialias=false) using the byte code interpreter (autohint=false). The results look as good as high quality bitmap fonts. On the other hand, most Fonts do not have good byte code interpreter instructions and look *very* ugly when rendered like this. I.e. for most fonts autohint=true and antialias=true gives best results. For fonts which do have good byte code instructions, it seems to be a matter of taste. Most users apparently do not like the bitmaps no matter how good they are and prefer to render these fonts with anti-aliasing as well. When rendering fonts which do have good byte code with anti-aliasing (antialias=true), the byte code apparently doesn't help much, to the contrary, it produces strange rendering artifacts. Therefore it is usually better to always use the autohinter (autohint=true) when rendering with anti-aliasing. --> <!-- Using the autohinter and anti-aliasing. This is a good default for most fonts. --> <match target="font"> <edit name="autohint"> <bool>true</bool> </edit> <edit name="antialias"> <bool>true</bool> </edit> </match> <!-- The following rule sets up black and white rendering with the byte code interpreter for a small list of fonts which are known to have good byte code and give bitmap quality results at small sizes. The pixelsize limit is set to '0' though, which effectively disables this rule by default because most users don't like that bitmap look and feel. If you like a bitmap look and feel of your desktop, copy this rule into your ~/.fonts.conf file and replace the '0' with non-zero pixelsize limit. Using '18' as the pixelsize limit is a good choice if you have the fonts in this list installed and like a bitmap look and feel. --> <match target="font"> <test name="family"> <string>Andale Mono</string> <string>Arial</string> <string>Comic Sans MS</string> <string>Georgia</string> <string>Impact</string> <string>Trebuchet MS</string> <string>Verdana</string> <string>Courier New</string> <string>Times New Roman</string> <string>Tahoma</string> <string>Webdings</string> <string>Albany AMT</string> <string>Thorndale AMT</string> <string>Cumberland AMT</string> </test> <test name="pixelsize" compare="less_eq"> <double>0</double> <!-- use a non-zero pixel size to enable this rule --> </test> <edit name="autohint"> <bool>false</bool> </edit> <edit name="antialias"> <bool>false</bool> </edit> </match> I used 18 pixel as the limit, just as on MS Windows. A handful of users had requested to make this the default, but after I had done this, I received many complaints from other users, therefore I disabled this rule again by setting the limit to 0 pixels. Although this style is the default on MS Windows XP, most Linux users apparently do not like it.

...

I want to disable embedded bitmaps for Japanese by default only if we are *sure* that the majority of users prefers the outlines. How to find out?

suse-linux-ja?

I'll ask there. -- Mike FABIAN http://www.suse.de/~mfabian 睡眠不足はいい仕事の敵だ。