[gs-bugs] [Bug 691912] New: Observations about font embedding

[bugzilla-daemon at ghostscript.com]

http://bugs.ghostscript.com/show_bug.cgi?id=691912

           Summary: Observations about font embedding
           Product: Ghostscript
           Version: 9.00
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P4
         Component: PDF Writer
        AssignedTo: ken.sharp at artifex.com
        ReportedBy: pipitas at googlemail.com
         QAContact: gs-bugs at ghostscript.com
   Estimated Hours: 0.0


I've been playing with 't1testpage' which consumes a .pfb fontfile as parameter
and creates PostScript output representing a (supposedly complete) sample of
glyphs. 

't1testpage' has this "--help" description: 

   "‘t1testpage’ creates a PostScript proof document for the specified Type 1 
    font file and writes it to the standard output. The proof shows every glyph 
    in the font, including its glyph name and encoding." (The PostScript output 
    has the font embedded)."

OK, I pipe this result to a Ghostscript commandline for pdfwrite-ing an output
PDF. This works, so far so good.

I tweaked the Ghostscript parameters a bit to get full vs. subset embedding:

  (1) -dEmbedAllFonts=true -dSubsetFonts=false \
      -c ".setpdfwrite <</AlwaysEmbed [/${current_font}]>> setdistillerparams"
  (2) -dEmbedAllFonts=true -dSubsetFonts=true \
      -c ".setpdfwrite <</AlwaysEmbed [/${current_font}]>> setdistillerparams"

(1) indeed seems to have the font fully embedded (confirmed by Acroread's file
properties display); filesize is 216k. 
(2) seems to have font subsetted (confirmed by Acroread's file properties
display); filesize is 77k.

This same thing happens for every single font I try.

But there is no visual difference at all between the 2 files (as you'd expect). 

My questions are:

 * Why would the "subset" file be so much smaller than the "full embed" file? 
   (Remember, since the PDF is supposed to contain the complete set of the 
   font's glyphs, I'd assume 'subset == fullset'

 * Should I assume that the glyph sample is not completely contained after all?

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