[PyKDE] imageformat plugin support in PyQt4?

[Tara Hernandez]

Duh.

Qt 4.1.3, 64 bit Fedora Core 2

David Boddie wrote:
> On Thu Oct 19 00:32:26 MEST 2006, Tara Hernandez wrote:
>
>   
>> I'm trying to get jpeg image support going via PyQt4, to no luck.  For 
>> example, the following C++ code:
>>     
>
> [...]
>
>   
>>     for (QList<QByteArray>::const_iterator
>>         i = formats.constBegin(); i != formats.constEnd(); ++i)
>>         cout << string(*i) << "\n";
>>
>> returns the expected list:
>>
>>     bmp
>>     jpeg
>>     jpg
>>     mng
>>     pbm
>>     pgm
>>     png
>>     ppm
>>     xbm
>>     xpm
>>     
>
> OK. I'm guessing that this is with Qt 4.1, but you don't say which platform
> you're using.
>
>   
>> But my python code (using the aforementioned Qt distrib) trying to do 
>> the same thing skips both jpeg and mng formats:
>>     
>
> [...]
>
>   
>> print "Supported:"
>> for type in QImageReader.supportedImageFormats():
>>    print " ",type
>>
>> Supported:
>>   bmp
>>   pbm
>>   pgm
>>   png
>>   ppm
>>   xbm
>>   xpm
>>     
>
> OK.
>
>   
>> Everything I've found on the subject says if it's in the C++ side, it 
>> should be in the Python side as well, but that really doesn't appear to 
>> be the case with regards to plugin supported image formats.
>>     
>
> It should work. My installed versions of Qt (4.1.4 and 4.2.0) have plugins
> for JPEG and MNG (and SVG in 4.2.0), and these appear in the list of
> supported image formats.
>
>   
>> Any clues for me?  Hopefully this is just me missing the appropriate 
>> documentation...
>>     
>
> Hopefully, you're just seeing the problem described in this post to
> qt-interest:
>
>   http://lists.trolltech.com/qt-interest/2005-11/thread00422-0.html
>
> Basically, you need to create a QApplication instance before you check
> for the available image format plugins.
>
> The reason I didn't see this problem was because I'm using a Python
> interpreter with support for Qt's event loop. It creates a QApplication
> instance on start-up.
>
> If you still see the same problem after instantiating a QApplication, it's
> worth checking that PyQt is built against the same version of Qt that you
> used in the first example above, just to eliminate the possibility that
> you're looking at different versions of Qt.
>
> Beyond that, I tried to think about various ways in which plugins might not
> load but they all seemed quite contrived. If you are still having problems
> with this, can you provide some details about your PyQt and Qt
> configurations?
>
> David
>
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