[Fontconfig] [Behdad] Re: How can I store FC_MATRIX object to cache file?

[Behdad Esfahbod]

Can you file a bug with reference to these details please?

behdad

On 09/03/10 03:50, mpsuzuki at hiroshima-u.ac.jp wrote:
> On Thu, 02 Sep 2010 16:44:35 -0400
> Behdad Esfahbod <behdad at behdad.org> wrote:
>> Can you explain more why the PANOSE values are needed?  And, do we need to
>> allow users to query based on them, or just having them in the cache?
> 
> In some popular document formats, like PDF, SVG, ODF and OOXML,
> Panose values are embedded to give the hint for font substitution.
> ==================================================================
> PDF 
> ---
> PDF Reference 6th edition (for PDF version 1.7)
> 5.7.2 Font Descriptors for CIDFonts
> 
> 	see the description for "Style" entry which
> 	includes 2 bytes from OS/2.sFamilyClass,
> 	10 bytes from OS/2.Panose.
> 
> SVG
> ---
> http://www.w3.org/TR/2003/REC-SVG11-20030114/fonts.html
> 20.8.3 The `font-face' element
> 
> 	there are many elements inherited from CSS2,
> 	including Panose.
> 
> ODF
> ---
> http://docs.oasis-open.org/office/v1.1/OS/OpenDocument-v1.1.pdf
> 14.6.1 CSS2/SVG Font Descriptors
> 
> 	ODF adopted the elements for the fonts from
> 	CSS2 and SVG, so even the font is for the text
> 	(not for embedded scalable graphics), it may
> 	have Panose value in the svg:panose-1 attribute.
> 	
> OOXML
> -----
> ISO/IEC 29500-1:2008
> 17.8.3.13 panose1 (Panose-1 Typeface Classification Number)
> 
> 	OOXML have several font properties (GDI parameters,
> 	Panose, and supported unicode range). In 17.8.2 Font
> 	Substitution, there is a list of properties to be
> 	used in the font substitution, and panose is described
> 	as the highest priority.
> 
> PCL
> ---
> "PCL 5e Technical Quick Reference Guide"
>   http://h20000.www2.hp.com/bc/docs/support/SupportManual/bpl13205/bpl13205.pdf
> "PCL5 Comparison Guide"
>   http://h20000.www2.hp.com/bc/docs/support/SupportManual/bpl13206/bpl13206.pdf
> 
> 	PCL5 selects the font by giving Panose parameters
> 	sequentially and narrowing down the candidates,
> 	see PCL 5e Technical Quick Reference Guide p 11-15.
> 
> 	See table 1-1 "PCL5 Feature Support Matrix" in
> 	page 1-12 PCL5 Comparison Guide, many PCL5
> 	implementations support the feature to narrow
> 	down by Panose parameters.
> 
> 	Also PCL6 (PCL XL) supports the feature by
> 	giving a string of PCL5 commands to PCLSelectFont
> 	attribute.
> ==================================================================
> In addition, current fontconfig does not have easy element to
> be related with CSS's 5 family classification (serif, sans-
> serif, cursive, fantasy). I think getting FamilyClass & Panose
> values from fontconfig cache may be helpful, because the
> application don't have to open a face, load OS/2 table,
> check FamilyClass/Panose values, close a face.
> 
> The font selection by the matching of familynames & charsets
> leaves a room for an improvement, because severeal documents
> formats (and CSS) have these properties in the documents.
> 
> --
> 
> The query based on these properties is arguable. The algorithm
> to evaluate "best matching" font by Panose is not specified
> in Panose specification paper. If exactly same, it is ok - but if
> different, it is arguable how the similarity should be evaluated.
> Some people want to give the highest priority to serif/sans-serif
> contrast, others want to give it to weight similarity. At present,
> I don't have good idea that everybody think it as acceptable.
> 
> Thus, I think just giving the APIs to provide these properties
> (FamilyClass, Panose, etc) is appropriate starting point. It
> is still convenient for fontconfig client applications because
> they can reduce the costs to open/check/close many font files
> by themselves.
> 
> # In fact, in PCL5, the priority of each bytes in Panose is user
> # controllable.
> 
> Behdad, could I answer to your question? If I'm misunderstanding
> what I was requested, please give me one more chance.
> 
> Regards,
> mpsuzuki
> 
> P.S.
> If putting so many data to fontconfig is bad idea, please let me
> know.
> 
>> On 09/02/10 14:24, mpsuzuki at hiroshima-u.ac.jp wrote:
>>> Hi,
>>>
>>> How can I store FC_MATRIX object to cache file?
>>>
>>> --
>>>
>>> Now I'm trying to add some properties to fontconfig database,
>>> which are taken from OS/2 and PCLT tables in OpenType: like
>>> sFamilyClass (so-called IBM family classification), Panose etc.
>>> They are useful to guess whether typeface is typographic/scriptic,
>>> serif/sans-serif, proportional/fixed-pitch etc. My original
>>> motivation is an improvement of the font substitution in poppler.
>>> For detail, please find:
>>>
>>> 	https://bugs.freedesktop.org/show_bug.cgi?id=5168
>>>
>>> Panose in OpenType is a collection of 10 parameters, and
>>> all parameters are expressed by 8bit. 80bit is too large
>>> to pack into double integer, so I have to consider what is
>>> the best way to store such in FcPattern. I think there are
>>> 3 options:
>>>
>>> 1) Name all parameters and store separately, aslike,
>>> adding 10 types to FcObjectTypes: FC_OS2_PANOSE_0,
>>> FC_OS2_PANOSE_1, ...
>>>
>>> # The name of each byte is different from OpenType spec
>>> # and its reference, so I don't use OpenType spec name
>>> # like FC_OS2_PANOSE_FAMILYTYPE.
>>>
>>> 2) ASCII-fy 10 parameters to NULL-terminated string,
>>> and use as a string type property.
>>>
>>> 3) Define new data type, a structure including 10 members
>>> and add "FcTypePanose" to FcType.
>>>
>>> --
>>>
>>> About 1), it's easy for me to write such patch and for
>>> users to use, but the addition of 10 objects may be too
>>> much, because current variety of the object type is 41.
>>>
>>> About 2), it's easy for me to write such patch but tricky
>>> for users to use, because it is requred to decode from
>>> ASCII string to original data.
>>>
>>> About 3), it's easiest for users. So I have to consider
>>> about this option.
>>>
>>> Checking the source code of fontconfig, FcMatrix data
>>> type looks similar (a structure with fixed length), but
>>> it seems that the data typed FcMatrix cannot be stored
>>> in cache file. I inserted FcMatrix object to FcPattern
>>> and tried to save it in cache file, but it seems that
>>> FcMatrix typed data cannot be saved (fc-cat can read
>>> object type but cannot read value).
>>>
>>> The code for FcString, FcCharSet and FcLangSet are
>>> variable length data and have many works. So I want to
>>> know how I can store FcMatrix typed data to cache file.
>>>
>>> Regards,
>>> mpsuzuki
>>>
>>> P.S.
>>> If option 1) or 2) are acceptable for fontconfig maintainers,
>>> I will do so.
>>>
>