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Re: How to get glyph metric info of CID-keyed font?

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On 2017/4/10 15:13, ken wrote:
> In article <occp90$tl6$1@dont-email.me>, jszhao@yeah.net says...
>>
>> Hi there,
>>
>> I am using R (www.r-project.org) to plot statistical figure. I prefer to
>> use postscript device. Instead of Type1 fonts, I hope to use Truetype or
>> Opentype fonts in my figure,
>
> You cannot directly use TrueType fonts or OpenType fonts with a
> PostScript interpreter, because PostScript deos not support either
> TrueType or OpenType.
>
> Language Level 3 PostScript interpreters can use both type 42 (which are
> TrueType fonts 'bundled up' in a way which PostScript interpreters can
> understand) and CFF font outlines. Earlier language levels did not
> support CFF and may not support type, support for CFF was added with
> level 3, and support for type 42 was introduced as a supplement to the
> original level 2 sepcification. CIDFonts were also added (in version
> 2015 as I recall) during the lifetime of language level 2.
>
> Note (1) that for OpenType fonts, you would need to check the outline
> type of the font and then supply either a Type 42 (TrueType) font or a
> CFF font, in each case extracting the relevant data from the font.
>
> Note (2) Ghostscript *can* make use directly of both TrueType and
> OpenType fonts as substitutes for missing fonts. However this involves
> the interpreter 'guessing' at certain information which would normally
> be presented unambiguously in the tytpe 42 font. So sometimes it will
> get it wrong.
>
>
>> that means I have to use CIDFont function.
>
> Nope. Type 42 fonts are not CIDFonts. A CIDFont may have a number of
> different kinds of outlines, including type 42 outlines, but its
> entirely possible to have a type 42 font which is not a CIDFont.
>
> The same is also true for CFF outlines (OpenType fonts may have CFF
> outline data, instead of TrueType.
>
>
>> I read the help page of CIDFont function which state that the CID-keyed
>> font are intended only for use for the glyphs of East Asian languages
>> that are all treated as filling the same bounding box.
>
> No, sorry, that's not really true either. It is the case that the
> original impetus for development of CIDFonts was the complexity of the
> written forms of Asian languages, but nowadays CIDFonts are used
> extensively for all languages.
>
>
>> In the source
>> code of ``devPS.c'', the ascent, descent and width of glyph is assumed,
>> and not calculated based on actual font. In fact, I think, R can't get
>> the exact metric info for the glyph in CID-keyed font, and can't typeset
>> correctly or beautifully. It seems that R can't find or access to the
>> actual font. After output to a postscript file, Ghostscript with
>> correctly configuration can render the figure correctly.
>>
>> My question is how to get glyph metric info of CID-keyed font in C code
>> directly or by call Ghostscript?
>
> You can interpret the font. There is no equivalent of the '.pfm' files
> that were once supplied with Type 1 fonts and contained the metrics of
> the glyphs.
>
> Ghostscript, like any font rendering engine, *must* interpret the font
> in order to render it. The font (whether TrueType or CFF outlines) will
> contain its own set of metrics which cover all the glyphs in the font,
> each glyph will additionally contain information such as the BoundingBox
> (or hsbw, Horizontal Side Bearing and Width) information in the glyph
> description.
>
> Ghostscript (mostly) uses FreeType for its font rendering, I would think
> that the simplest approach for you would be to do the same.
>
> I'm afraid I can't offer you any help with R, I know nothing about it.
>
> 				Ken
>

Thank you very much for the reply and explanation. I now use cairo_ps 
function in R to plot, which use cairo graphics API and can use CFF 
fonts directly.

Best,
Jinsong

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Thread

How to get glyph metric info of CID-keyed font? Jinsong Zhao <jszhao@yeah.net> - 2017-04-09 15:56 +0800
  Re: How to get glyph metric info of CID-keyed font? ken <ken@spamcop.net> - 2017-04-10 08:13 +0100
    Re: How to get glyph metric info of CID-keyed font? Jinsong Zhao <jszhao@yeah.net> - 2017-04-18 11:32 +0800

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