read part of jpeg file by pure python

[Laurent Pointal]

Pacino a écrit :
> Hi, everyone,
> 
> I am wondering whether it's possible to read part (e.g. 1000*1000) of
> a huge jpeg file (e.g. 30000*30000) and save it to another jpeg file
> by pure python. I failed to read the whole file and split it, because
> it would cost 2GB memory.
> 
> Can anyone help me? Any comments would be appreciated.
> 
> Thanks.
> 
> Robert
> 

Just reading parts of the *file* is easy (see tell() seek() and read()
methods on files).
But to extract a part of the *picture*, you must uncompress the picture
in memory, grab the sub-picture, and save it back - generally with
compression. I can't see how you can bypass the uncompress/compress
phases and the corresponding memory use.

A+

Laurent.