[File] [PATCH] Magdir/font X11 SNF font misidentfies DEGAS bitmap BIGSPID.PI1

[Christos Zoulas]

Committed, thanks!

christos

> On Nov 23, 2021, at 1:20 PM, Christos Zoulas <christos at zoulas.com> wrote:
> 
> Signed PGP part
> Committed, thanks!
> 
> christos
> 
>> On Nov 22, 2021, at 5:55 PM, Jörg Jenderek <joerg.jen.der.ek at gmx.net> wrote:
>> 
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>> Hello,
>> 
>> some days ago i installed an older Adobe software with some fonts.
>> So i was checking some other font stuff.
>> 
>> When running running file command version 5.41 on DEGAS images
>> examples i get an output like:
>> BIGSPID.PI1: X11 SNF font data, MSB first
>> 
>> Furthermore with --extension option only 3 character sequence ???
>> is shown.
>> 
>> For comparison reason i run the file format identification utility
>> TrID ( See https://mark0.net/soft-trid-e.html). The example is not
>> recognized as font (See appended trid-v.txt.gz). But in the TrID
>> database exist a definition snf-x11-lsb.trid.xml for the little
>> endian variant. TrID list the used file name extension SNF.
>> 
>> Luckily i found on file formats archive team web site a page about
>> SNF (Server Normal Format). There also a link to source header file
>> snfstr.h with specifications is mentioned.
>> So these informations are now expressed by additional comment lines
>> inside Magdir/fonts like:
>> # URL:		http://fileformats.archiveteam.org/wiki/SNF
>> # Reference:	https://cgit.freedesktop.org/xorg/lib/libXfont/
>> #		tree/src/bitmap/snfstr.h
>> # Reference:    http://mark0.net/download/triddefs_xml.7z
>> #		defs/s/snf-x11-lsb.trid.xml
>> 
>> In current version big endian SNF fonts examples are described by
>> lines like:
>> 0	belong	00000004	X11 SNF font data, MSB first
>> !:mime	application/x-font-sfn
>> 
>> So 4 bytes are used for recognition, but 3 are zero. So this is no
>> so unique enough. The same problem exist for the little endian
>> variant which i fixed in February 2013. So according to
>> documentation i also
>> checked for second version stamp at offset 104 which is the same as
>> the first version at the beginning. So this now becomes like:
>> 0	belong	00000004
>>> 104	belong	00000004		X11 SNF font data, MSB first
>> !:mime	application/x-font-sfn
>> !:ext	snf
>> By this additional second test line misidentified Atari DEGAS low
>> resolution bitmap BIGSPID.PI1 now is skipped.
>> 
>> After applying the above mentioned modifications by patch
>> file-5.41-fonts-snf.diff then the misidentification vanish. This
>> now looks like:
>> BIGSPID.PI1: data
>> 
>> I hope my diff file can be applied in future version of file utility.
>> 
>> I will try to add magic for DEGAS bitmap images in the future, but
>> it is a little bit difficult because such images have no real
>> strong magic pattern. So i must look for sufficient test lines.
>> 
>> With best wishes
>> Jörg Jenderek
>> - --
>> Jörg Jenderek
>> 
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>> <file-5_41-fonts-snf_diff.DEFANGED-274><file-5_41-fonts-snf_diff_sig.DEFANGED-275><trid-v.txt.gz>--
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