Re: [ft-devel] [FYI] MingLiU identifier

[mpsuzuki]

In general scope, I think, you raised a concern that
the checksum in TTF header is too simple (it's a sum
of 32-bit values of the table) to guarantee the identity.
It's reasonable.

If I check the fonts bundled to Microsoft Windows,
Mac OS (Classic & OS X), and distributed in GNU/Linux
distribution and I find no conflict, is it sufficient
guarantee? If not, I cannot access wider coverage
of the fonts, so, the possible solution would be...

1) identify by family name comparison is used too,
   and add a fallback by sfnt table checksum.

2) in addition to the tag-name of the table and
   the checksum, the length should be checked.

3) if it's still insufficient... should we use
   our own hash value instead of the checksum
   in sfnt header.

In narrower scope, I think, PMingLiU bundled to
Microsoft Office for Mac are not needed to be
hinted. I attached the PDF made on them, including
bundled PMingLiU. Even if it's rendered without
hinter, the result is not broken (in comparison
with pre-Windows XP cases).

Could you tell me more about the range of your
concern?

Regards,
mpsuzuki


On Wed, 17 Nov 2010 06:49:44 -0500
David Bevan <address@hidden> wrote:

>
>Some of these tables are very short (a total of only 44 bytes on the Mac), so 
>what is the likelihood that they match tables in other fonts that don't 
>require TT hinting?
>
>We need some guarantee that comparing these values will uniquely identify the 
>relevant fonts.
>
>David %^>
>
>
>
>-----Original Message-----
>From: address@hidden [mailto:address@hidden On Behalf Of address@hidden
>Sent: 17 November 2010 02:29
>To: freetype-devel
>Subject: [ft-devel] [FYI] MingLiU identifier
>
>Hi all,
>
>Since freetype-2.4.3, TrueType hinter is enabled for
>the fonts without family name. It was a fallbacking
>solution of MingLiU embedded in PDF, without family
>name (according to Type42 spec, name table is optional,
>so embedded TrueType in PDF may lack family name).
>
>Recently, Gentoo people request to revert it to disable
>the hinter by default, because it makes TimesNewRoman
>embedded by Mac OS X Quartz ContextPDF (a generic
>framework in Mac OS X to generate PDF document) ugly.
>
>Thus, now I'm trying to identify problematic fonts
>which cannot be readable if rendered without hinter,
>by the checksum (or the pair of checksum & length?)
>of required table for Type42. cvt, fpgm and prep are
>the candidates because their content is tightly bound
>to glyf programs, so they are usually preserved in
>the TrueType subsetting process.
>
># the proof of idea was posted at:
># http://lists.nongnu.org/archive/html/freetype-devel/2010-08/msg00019.html
>
>Here I collected the checksums of various versions
>of MingLiU. During the check, I found that recent
>MingLiU (post-Vista, and Microsoft Office for Mac)
>don't cause broken shape issue anymore.
>
>I checked various versions mentioned at:
>  http://zh.wikipedia.org/zh/%E6%96%B0%E7%B4%B0%E6%98%8E%E9%AB%94
>From the result, I think, the checksum of cvt/fpgm/prep
>can be classified into 2 groups, older & newer, I'm
>happy to see that we (may) don't have to maintain
>long list of the checksum for all versions of MingLiU.
>
>Regards,
>mpsuzuki
>
>Microsoft Windows NT 4.0: ver 2.00 (1996-May-15, second release)
>               tag cvt  offset 0x0023dc7c length 0x000002e4 checkSum 0x05bcf058
>               tag fpgm offset 0x0023df60 length 0x000087c4 checkSum 0x28233bf1
>               tag prep offset 0x005fb248 length 0x000001e1 checkSum 0xa344a1eb
>
>Microsoft OfficeXP Proof Kit: ver 3.00
>               tag cvt  offset 0x0038bb94 length 0x000002e4 checkSum 0x05bcf058
>               tag fpgm offset 0x0038be78 length 0x000087c4 checkSum 0x28233bf1
>               tag prep offset 0x0082fe78 length 0x000001e1 checkSum 0xa344a1eb
>
>Microsoft Windows XP: ver 3.21
>               tag cvt  offset 0x003a101c length 0x000002e4 checkSum 0x05bcf058
>               tag fpgm offset 0x003a1300 length 0x000087c4 checkSum 0x28233bf1
>               tag prep offset 0x0086a004 length 0x000001e1 checkSum 0xa344a1eb
>
>(Microsoft Office for Mac v.X: MingLiU is not bundled)
>Microsoft Office for Mac 2004: ver 4.55
>Microsoft Office for Mac 2008: ver 4.55
>Microsoft Office for Mac 2011: ver 4.55
>               tag cvt  offset 0x0001cdf8 length 0x00000008 checkSum 0x00000000
>               tag fpgm offset 0x0001cdd0 length 0x00000011 checkSum 0xf40ddf13
>               tag prep offset 0x0001cde4 length 0x00000013 checkSum 0x6286ee0a
>
>Microsoft Windows Vista: ver 6.02
>               tag cvt  offset 0x004a437c length 0x00000008 checkSum 0x00000000
>               tag fpgm offset 0x004a4384 length 0x00000011 checkSum 0xf40ddf13
>               tag prep offset 0x019fc218 length 0x00000013 checkSum 0x6286ee0a
>
>Microsoft Windows 7: ver 7.00
>               tag cvt  offset 0x00499f78 length 0x00000008 checkSum 0x00000000
>               tag fpgm offset 0x00499f80 length 0x00000011 checkSum 0xf40ddf13
>               tag prep offset 0x019f4064 length 0x00000013 checkSum 0x6286ee0a
>
>_______________________________________________
>Freetype-devel mailing list
>address@hidden
>http://lists.nongnu.org/mailman/listinfo/freetype-devel
>

MingLiU-QuartzPDF.pdf
Description: Adobe PDF document