[Qgis-developer] Exporting a raster layer

[Etienne Tourigny]

On Wed, Jan 16, 2013 at 6:54 AM, Radim Blazek <radim.blazek at gmail.com> wrote:
> On Sun, Jan 13, 2013 at 5:52 PM, G. Allegri <giohappy at gmail.com> wrote:
>> In Qgis master I think you could use QsgRasterFileWriter [1], for the raster
>> providers which support writing,e.g. GDAL.
>
> Yes, the QsgRasterFileWriter is higher level class for raster writing,
> it is using lower level QgsRasterDataProvider::write(). Current
> implementation of raster writing support was especially written for
> "raster save as", it may appear that it has to be extended a bit to be
> used as output of analytical tools.
>
> The QsgRasterFileWriter is reading/writing in parts specified by
> setMaxTileWidth(), setMaxTileHeight(). This mechanism could also be
> used for data processing especially if an underlying module is not
> optimized for large data sets (e.g. keeps all data in memory). OTOH,
> it may cause problems on tile borders if an algorithm depends on
> neighbour pixels in which case it would be necessary to process
> tile+buffer, but the problem is to find the buffer size for each
> module/options.
>
> The QsgRasterFileWriter is reading data from QgsRasterPipe, from its
> last QgsRasterInterface. However, it is also using some info from
> original data source, for example original data type, so that it can
> optimize output data type. Now it works just for saving of existing
> rasters, probably we have to think it over again for use with
> analytical tools.
>
> The most obvious way to write raster from SEXTANTE using existing
> support in core/providers would  be to implement QgsRasterInterface
> representing SEXTANTE output. What do you think about that?
>
> In which form are the data you need to write - format, file/memory,...?
>
> It would be good to use also the same QgsRasterLayerSaveAsDialog used
> for raster saving, but maybe it has too many options?

IMHO the raster save as dialog should be used in the sextante output
as well as in gdaltools.  If it has too many options, perhaps it could
be re-designed to have "simple" and "expert" modes.

Regarding the integration of the save as dialog in gdaltools, I had
some interaction with Giuseppe Sucameli  but we got sidetracked, it
would be nice to finish this before 2.0.

Etienne

>
> Radim
>
>> AFAIK in Qgis 1.8 there's no mechanism to do that.
>>
>> giovanni
>>
>> [1] http://www.qgis.org/api/classQgsRasterFileWriter.html
>>
>> Sent from Nexus
>>
>> Il giorno 13/gen/2013 17:10, "Victor Olaya" <volayaf at gmail.com> ha scritto:
>>
>>> Hi all
>>>
>>> I have just implemented a new mechanism in SEXTANTE to make handling
>>> of file formats more clear and easy. Now, no matter what provider is
>>> creating a vector layer, all formats supported by QGIS can be
>>> selected, without requiring anything special added to the algorithm
>>> provider. SEXTANTE takes care of converting if needed.
>>>
>>> I want to implement the same thing for raster layers, but I do not
>>> know how to export a raster layer into a given format (except by
>>> calling GDAL translate), and I need it for that.. Can any one give me
>>> an idea or point me to some code to do that?
>>>
>>> Thanks in advance!
>>>
>>> Victor
>>> _______________________________________________
>>> Qgis-developer mailing list
>>> Qgis-developer at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/qgis-developer
>>
>>
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