Re: unable to open jpg file

[James Cloos]

File(1)'s magic file says this, for detecting jpegs:

,----[ excerpt from /usr/share/misc/file/magic ]
| # JPEG images
| # SunOS 5.5.1 had
| #
| #       0       string          \377\330\377\340        JPEG file
| #       0       string          \377\330\377\356        JPG file
| #
| # both of which turn into "JPEG image data" here.
| #
| 0       beshort         0xffd8          JPEG image data
| >6      string          JFIF            \b, JFIF standard
`----

So rather than searching for JFIF or EXIF emacs should test the first
two or four octets for the real magic cookie.

Magic.mime(4), used to determine the MIME type of a file, also only
tests the first two octets for 0xff and 0xd8.  It should be enough,
then, for Emacs to test only those two octets as well.

Incidently, file(1) is under a 2-clause BSD-style license; incorporating
the magic.mime file and using that to determine how to open files might
make for a more robust -- or at least well-tested -- system.

-JimC
-- 
James Cloos <address@hidden>         OpenPGP: 1024D/ED7DAEA6