Hofmann Johannes wrote:
> On Wed, Apr 22, 2009 at 01:14:29AM -0700, Albrecht Schlosser wrote:
...
>> "The only additional requirement" means for me that this is a requirement
>> only for JFIF, but not for JPEG itself.
>>
>> If the intention in the original code was to test for JFIF, then it
>> should have checked for exactly four bytes and the APP0 marker in the
>> fourth byte (and maybe the following "JFIF\0" as well) and not a range.
> 
> I think this is because it also want's to accept Exif files
> (http://www.Exif.org/specifications.html).
> They start like this:
> 
> 00000000  ff d8 ff e1 3a 3b 45 78  69 66 00 00 4d 4d 00 2a |ÿØÿá:;Exif..MM.*|
> 
> But Exif also requires it's marker to be first right after the SOI.
> So I now think Michael is right and exiv2 should be fixed instead.

I don't think so, but you may ask them anyway. I'm curious what they
will reply.

Exif is only another subset (specialization) of the general
JPEG format:

"The file-recording format is based on existing formats. Compressed files
are recorded as JPEG (ISO/IEC 10918-1) with application marker segments
(APP1 and APP2) inserted. Uncompressed files are recorded in TIFF ..."

Albrecht
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