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Re: [ft-devel] Understanding Type1 fonts

From: George Williams
Subject: Re: [ft-devel] Understanding Type1 fonts
Date: 09 Jan 2008 07:01:23 -0800

On Wed, 2008-01-09 at 00:24, Donn wrote:
> .PFA files
> These are a new twist, just found one today. I do not know if they also get 
> matched with some metric file. I see many .AFM files around and in one 
> folder:
PFA files contain exactly the same data as a PFB, they are a hex (ASCII)
dump rather than a binary one.

> Essentially: Is an AFM or a PFM file needed *at all*? 
AFM files contain:
   bounding box and advance width data
        These can be regenerated from what's in the PF[AB]
   kerning data
        These are not stored in the PF[AB]
   ligature data
        These are not stored in the PF[AB]
   potentially data on glyph composites. This is rare
        Not stored in the PF[AB]
So AFM files contain useful info not in the PF[AB], but their presence
is not required.

I can't remember what goes in PFM files.

> Ok +1 vote for "AFM and PFM" as non-essential to a Gnu/Linux system.
If you throw them out you lose all your kerning.

> How important do you thing that extra data is on a modern Gnu/Linux 
> system. Without going into C code, to what extent does Freetype work
> around when it does not find a metric file for a given font file? 
It simply won't provide any kerning information. So potentially your
quality degrades.

> So, I take it you would advise that the corresponding metric files
> should be in the same folder as the glyph files?

> Am I right to assume the links are:
> PFB --> PFM
> and
> PFA --> AFM
PFM is a microsoft binary representation of the same kind of data stored
in an AFM file (which is an adobe ascii representation). Either type of
file can be associated with either type of font.

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