[Image-SIG] General question on JPEG file format

[Fredrik Lundh]

ken wrote:

> This isn't really  a Python or PIL question, but I thought
> the people reading this particular list were likely to know
> the answer :-)

looks like we're all too busy...

> My understanding is that JPEG is really just a compression
> algorithm, and that what most people think of as JPEG files
> are actually JFIF files. From perusing the specs for a JFIF
> file, it also seems that JFIF makes provision for the inclusion
> of thumbnails and other metadata about the main image.

> However, I've never actually seen this used by picture
> viewers, creators, etc. /.../ Are there reasons this isn't
> commonly done with JPEG/JFIF files?

I think you just answered your own question ;-)

Very few applications support this, which is why very few
application writers bother to implement it...  (this also in-
cludes library writers like yours truly -- I cannot remember
seeing any widely used application that supports this, and
nobody has ever asked for JFIF metadata support for PIL...)

</F>