Re: Help,please !!!!!!!

[David Turner]

Hi Lidia,

  I've taken a deep look at tahoma.ttf and the ttf2pt1 source
  code..

  When creating the encoding for the Type 1 font, ttf2pt1 remaps
  some of the glyphs. Basically this means that:

    - tahoma.ttf contains a valid Unicode charmap, and doesn't
      define glyph images for codes 127 to 159 (this is in
      accordance to the specification)

    - when ttf2pt1 converts this font to Type 1, it remaps some
      characters because of some stupid restrictions in the Type 1
      format (i.e. no more than 256 character codes in an encoding)
      Basically, it tries to look for common unicodes above 256,
      see if they have a glyph, and if so, tries to place them
      in the "vacant" entries of the original charmap..

  For example, character code 136 in the Type 1 font ("circumflex")
  does not correspond to any valid Unicode value. Its glyph is
  however the same than the one for character code 0x2c6 in the
  original Tahoma font..

  I guess FreeHand does something similar..

  The .afm file correspond to the Type 1 font, and not to the
  charmap located in Tahoma.ttf. You cannot use it with a TrueType
  font because of this stupid remapping thing..

  The problem comes from the fact that charcodes are nearly just
  useless with Type 1 fonts, you really need to look at the list
  of glyph names and build a real Unicode charmap from these,
  over-riding the definition of the "encoding" dictionary.

  Hopefully, this is precisely what FreeType 2 does with Type 1
  fonts :-)

Hope its clear..

Cheers,

- David



Lidia Mirkin a écrit :
> 
>     Hello !
> Thank you very much about your reply.
> Scenario is following:
> 1.I read Tahoma.ttf using FreeType.Particulary , I read char widths from
> this font,
> using code below.TT_Get_CharMap_ID returns 0 for characters in range
> 125-160.
> and therefore , I get width = 0 for these characters.
> 2.After that , I embed this font  to PDF.
> 3.In FreeHand i make some example pdf with embedding the tahoma font, open
> PDF in some text editor and check character widths: for characters
> 125,126,127 they are 1000( default width) and for characters 127-160 they
> are not equal to 1000.
> 4.I used ttf2pt1 ( ttf2pfa ) tool in order to convert Tahoma.ttf to afm,pfa.
> Character widths inside .afm are same to those we get in FreeHand.
> 5.I don't read font from PDF.
> 6.I send you compiled ttf2pt1 and also project for MS-5.0.
> you can run this program by
> 
> ttf2pt1.exe <path to ttf file> <path to output files/name of output files>
> <example>
> tt2pt1.exe Tahoma.ttf Tahoma
> 
> 7.Also , I am sending  you generated .afm file.
> 
> It is clear , that I can use this program for my purposes , but I would like
> to know how
> can I do it by FreeType ( because , this library is very convenient for
> usage ).
>             thak you very much , Lidia.
> 
> > It's important to distinguish which fonts you're talking about..
> >
> >   - taking a "stock" font like tahoma.ttf, some **character codes** in the
> >     125 to 160 range correspond to glyph index 0 (this is normal
> >     for Latin-1 based encodings like Unicode).
> >
> >   - you compute the size of such characters as the one of glyph 0,
> >     which is here 1000
> >
> >   - when embedding the font with FreeHand, then reading it from the
> >     PDF (right ???), the same character codes will produce different
> >     widths !!
> >
> > My question is this:
> >
> > - Do these character codes map to glyph index 0 or not ?
> >   If not, FreeHand has modified the charmap within the font, and
> >   you're not reading the original font..
> >
> > - Do the embedded font still have a (3,1) charmap, or something
> >   different ??
> >
> > > ttf2pt1(ttf2pfa) get valid values....
> > >
> >
> > Does it get the "valid values" from the original font, or the
> > embedded one. It's really hard to see what you're speaking about,
> > we need a bit of clarification :-)
> >
> 
> Code:
> > for (i=0;i<n;i++)
> > >  {
> > >   if (error=TT_Get_CharMap_ID( face, i, &platform, &encoding ))
> > >    goto done_face;
> > >   if ( (platform == 3 && encoding == 1 ) )
> > >   {
> > >    TT_Get_CharMap( face, i, &charMap );
> > >    break;
> > >   }
> > > ....
> > >  }
> > >  for (i=0;i<=255;i++)
> > >  {
> > >   unsigned short char_index=TT_Char_Index( charMap, i );
> > >   TT_Get_Face_Metrics( face,
> > >                        char_index,
> > >                        char_index,
> > >                        NULL,
> > >                        temp,
> > >                        NULL,
> > >                        NULL );
> > >
> > >   font->widths[i]=(int)(temp[0]*scale_factor+0.5);
> > >  }
> > >
> > >
> 
>   
> ------------------------------------------------------------------------------------------------------------------------------------------------------
>                      Name: font_stuff.zip
>    font_stuff.zip    Type: Zip Compressed Data (application/x-zip-compressed)
>                  Encoding: base64