[Qgis-developer] Re: Raster providers

[Marco Hugentobler]

Hi Radim

> Hi Marco,
> the code is quite ugly at moment, I still keep old pieces of code
> commented.

That's fine. Like that, I won't get completely lost in the code :-)
 
> Regarding the reprojection, I would like to implement the approximate
> reprojection (similar to mapserver you showed me) in
> QgsRasterDataProvider::readBlock and overwrite it only in WMS
> provider. GDAL warp is too slow (as expected) and no way to speed it
> up AFAIK.

The approximate reprojection would be cool. Wouldn't it be better to implement 
it on rasterlayer level instead instead of QgsRasterDataProvider::readBlock? 
Like that, all providers would have reprojection capabilities (e.g. GRASS 
too).

With one of my favorite test dataset, I noted a problem with automatic 
assignment of nodata value and automatic insertion into the transparency list. 
In that case, the raster is a colortable map (byte) and has no nodata value. 
So 255 is set to transparent and the map appears completely different than 
expected...

Is it correct that the draw() method which returns QImage is not necessary 
anymore (or only for API compatibility for now)? Seems it can be handled quite 
nicely with QImage::bits(). 
In the future, it would be nice to have also support for create() and write() 
operations in the provider interface (and the gdal provider). Then I could 
port rastercalculator & terrain analysis to use the provider interface.

Regards,
Marco



> Radim
> 
> On Mon, Jan 10, 2011 at 9:36 AM, Marco Hugentobler
> 
> <marco.hugentobler at sourcepole.ch> wrote:
> > Hi Radim
> > 
> > Nice to see you are making good progresses with raster redesign!
> > 
> > Please give the dev team a bit time to review all the changes. I'd like
> > to have a closer look at the code. However, it's my first day back at
> > work, so it could take a few days until I can give feedback.
> > 
> > Regards,
> > Marco
> > 
> > Am Samstag, 8. Januar 2011, um 20.26:24 schrieb Radim Blazek:
> >> Hi all,
> >> new raster providers are ready for testing. The work is not yet
> >> finished but all the old functionality should be available. Current
> >> status:
> >> 
> >> - GDAL: on-the-fly reprojection via gdal warp, quite slow, I have not
> >> yet implemented the trick used in Mapserver Marco pointed me to.
> >> Please let me know, if you consider the speed at least acceptable for
> >> real work. The speed depends especially on output display size.
> >> 
> >> - GRASS: all the old functionality is back, the data are provided
> >> instead of just a picture so that it is possible to assign a style in
> >> QGIS like it was possible with GRASS via GDAL, reprojection is not yet
> >> implemented
> >> 
> >> - WMS: should work like before, the requested SRS does not yet follow
> >> current project projection
> >> 
> >> Please test the raster providers branch and let me know about problems:
> >> 
> >> svn co https://svn.osgeo.org/qgis/branches/raster-providers
> >> 
> >> I would like to merge the branch to trunk and continue the work in
> >> trunk.
> >> 
> >> Radim
> >> _______________________________________________
> >> Qgis-developer mailing list
> >> Qgis-developer at lists.osgeo.org
> >> http://lists.osgeo.org/mailman/listinfo/qgis-developer
> > 
> > --
> > Dr. Marco Hugentobler
> > Sourcepole -  Linux & Open Source Solutions
> > Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland
> > marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
> > Technical Advisor QGIS Project Steering Committee


-- 
Dr. Marco Hugentobler
Sourcepole -  Linux & Open Source Solutions
Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee