[Yanel-dev] [FYI] 'image/pjpeg' & 'image/x-png' pseudo MIME-types and how to work around them

[Guillaume Déflache]

Hi!

When uploading JPEGs using Internet Explorer, one often comes across the 
following problem: some images are sent by the browser with the 
Content-Type set to 'image/pjpeg' which is not an official (i.e. 
IANA-registered) MIME-type.
As usually one only rightfully tests for 'image/jpeg', these JPEGs 
usually get rejected as being in an unkonwn format.
The workaround is to test for this abnormal MIME-type and when possible 
reset it to 'image/jpeg' ASAP, or at least handle it as a regular JPEG.

This MIME-type was hacked as a kind of weak copyright protection 
measure, and only occurs when the image has embedded copyright and/or 
author metadata, cf. 
http://www.evolve.co.nz/how-to-fix-a-pjpeg-image-upload-error.html for 
the details.


Along the same lines old versions of Internet Explorer still uses the 
non-standard 'image/x-png' instead of the standard 'image/x-png'.

It may make sense to try to filter both of these in the Yanel servlet 
filter, as we already decorate some methods related to upload there 
IIRC, to solve these problems once and for all for all Yanel-based 
applications.


Microsoft kind of acknowledges these problems in 
<http://msdn.microsoft.com/en-us/library/ms775147(VS.85).aspx#_replace>.


HTH,
    Guillaume