[Qgis-developer] patch for qgsrasterlayer.cpp

Peter Ersts ersts at amnh.org
Tue Oct 2 10:17:53 EDT 2007


This looks good. There are a number these places where computations like 
this can be pulled out of loops to speed things up.

I will make sure these mods get into the raster branch.


Tim Sutton wrote:
> Hi Marco
> Thanks! There are actually many places we can optimise things. For one
> when we have a separate renderer class for each renderer type, we can
> avoid a lot of switches...
> Peter is now 'Raster Master' so I will defer the patch to him (if
> thats ok Peter?).
> Regards
> Tim
> 2007/9/28, Marco Hugentobler <marco.hugentobler at karto.baug.ethz.ch>:
>> Hi Peter and Tim,
>> While sitting in the train, I plaied a bit around with the methods
>> QgsRasterLayer::drawPallettedMultiBandColor and
>> QgsRasterLayer::drawMultiBandColor. I think that some multiplications and
>> comparison in the inner loop, which is executed appr. 800000 times during
>> each redraw, can be avoided or moved outside the loop. Especially,
>> QgsRasterLayer::drawPallettedMultiBandColor was much faster on my PC
>> afterwards.
>> Attached the patch. Please review and test, if I didn't break any existing
>> functionality.
>> Regards,
>> Marco
>> --
>> Dr. Marco Hugentobler
>> Institute of Cartography
>> ETH Zurich
>> Technical Advisor QGIS Project Steering Committee
>> marco.hugentobler at karto.baug.ethz.ch

Peter J. Ersts, Project Specialist
American Museum of Natural History
Center for Biodiversity and Conservation
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