[Qt-interest] Stream-oriented image conversion

[Jeffrey Brendecke]

Check into using the graphicsmagick tools along with QProcess.

http://www.graphicsmagick.org/

The docs for QProcess should give you the information you are looking for 
regarding chunking.

With images that large, the overhead of creating a new process is neglegible.

If the signal-slot mechanism for QProcess does not scale in this application, 
it seems you could create separate separate threads and work through the 
graphicsmagick libraries.

Jeffrey Brendecke

Managing Director
icanetix Software Systems and Consulting GmbH
Untere Hagenstrasse 26
91217 Hersbruck
Germany

Commercial Registry B 25317 Nuremberg, Germany
VAT-ID: DE250213502

--------------------
Date: Wednesday 23 June 2010 22:27
From: Jason H <scorp1us at yahoo.com>
To: qt-interest at trolltech.com
Cc: 
Subject: [Qt-interest] Stream-oriented image conversion
--------------------

> This seems like a no brainder, but I was wondering/hoping if someone could
> enlighten me.
>
> I need to convert very large images (usually just an array of bits, in
> various formats) to another format. These files are typically 80MB, but can
> go as high as 800MB+ and, adding to it, it is a multi-threaded environment,
> which means that I might have 10 or more images being converted at once.
>
> I was hoping with with Qt's QIODevice abstraction that I could set up some
> kind of streaming conversion where I can read 64k chunks and send them to a
> writer that will, when a tile is complete, process and write the tile in
> the new format. This way, with 10 thread on 80MB files, I only use 640k,
> rather than 800MB at a time, as 640k ought to be enough for anybody.
>
> Or, if there is some command line tools that already do it?
>
> Thanks!
>
>
>
>
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