[Qgis-developer] update plugin to QGIS 2.0

Fri Aug 2 08:04:09 PDT 2013

On Fri, Aug 2, 2013 at 11:58 AM, Otto Dassau <dassau at gbd-consult.de> wrote:
> Hi,
>
> thanks for the hint. And if I need the value of the raster? If I understand
> correctly, ident will always be 1, if I have a 1 band raster layer. But how
> can I get the value at QgsPoint(x,y) of the raster? I don't understand that
> from the value tool plugin.

no,  ident will be a dict with an element of key 1

you get exactly the fist band's value at the point with ident[1] .

the key of the map is the band number, and the value is the value (or
None if nodata/out of bounds)

so without any error checking you would do

ident = layer.dataProvider().identify(QgsPoint(x,y),QgsRaster.IdentifyFormatValue).results()
return ident[1]

cheers
Etienne

>
> In QGIS 1.8 I use :
>
> success, data = layer.identify(QgsPoint(x,y))
>    for band, value in data.items():
>    return value
>
> and in QGIS 2.0:
>
> ident = layer.dataProvider().identify(QgsPoint(x,y),QgsRaster.IdentifyFormatValue).results()
>    ?
>
> Thanks again
>
> Otto
>
>
> Am Fri, 2 Aug 2013 08:50:08 -0300
> schrieb Etienne Tourigny <etourigny.dev at gmail.com>:
>
>> from the api
>> http://www.qgis.org/api/classQgsRasterIdentifyResult.html#a8537d25fdff215e7e9650b71a0a16783
>>
>> results() returns a QMap<int, QVariant> (one item for each band), it
>> does not return a tuple, so you should actually call
>>
>> ident =
>> layer.dataProvider().identify(QgsPoint(x,y),QgsRaster.IdentifyFormatValue).results()
>>
>> and then test that ident is not empty (i,e. ident is not None and
>> ident.iterkeys() is not None)
>>
>> for each band, if the point is outside of the raster extent or is
>> nodata, the value will be a null QVariant (i.e. QVariant()) which in
>> python is None.
>>
>>
>> cheers
>> Etienne
>>
>> On Fri, Aug 2, 2013 at 7:13 AM, Otto Dassau <dassau at gbd-consult.de> wrote:
>> >
>> > Hi,
>> >
>> > thanks for your hints, I think I am on the right track now. I had a look
>> > at the value tool plugin and tried to adapt the method accordingly:
>> >
>> > def sampleRaster20(self, layer, x, y):
>> >    #success, data = layer.dataProvider().identify(QgsPoint(x,y))
>> >    success, data =
>> > layer.dataProvider().identify(QgsPoint(x,y),QgsRaster.IdentifyFormatValue).results()
>> > for band, value in data.items(): return value
>> >
>> > But now I get another error message
>> >
>> >  File
>> >  "/home/dassau/.qgis2/python/plugins/weibullanalyse/weibullanalysedialog.py",
>> >  line 448, in printValue self.showValues() File
>> >  "/home/dassau/.qgis2/python/plugins/weibullanalyse/weibullanalysedialog.py",
>> >  line 454, in showValues self.plot() File
>> >  "/home/dassau/.qgis2/python/plugins/weibullanalyse/weibullanalysedialog.py",
>> >  line 526, in plot w =
>> > float(self.sampleRaster(self.InRastW.currentText(), self.xCoord,
>> > self.yCoord))/10 File
>> > "/home/dassau/.qgis2/python/plugins/weibullanalyse/weibullanalysedialog.py",
>> > line 300, in sampleRaster return self.sampleRaster20(layer, x, y) File
>> > "/home/dassau/.qgis2/python/plugins/weibullanalyse/weibullanalysedialog.py",
>> > line 285, in sampleRaster20 success, data =
>> > layer.dataProvider().identify(QgsPoint(x,y),
>> > QgsRaster.IdentifyFormatValue ).results() ValueError: need more than 1
>> > value to unpack
>> >
>> > Do you have an idea for this, too?
>> >
>> > Thanks
>> > Otto
>> >
>> > Am Thu, 1 Aug 2013 16:00:08 -0300
>> > schrieb Etienne Tourigny <etourigny.dev at gmail.com>:
>> >
>> > > Have a look at the source of the value tool plugin, it calls the
>> > > identify() method and has been updated to 2.0 api.
>> > >
>> > > Etienne
>> > >
>> > > On Thu, Aug 1, 2013 at 1:58 PM, Otto Dassau <dassau at gbd-consult.de>
>> > > wrote:
>> > >
>> > > > Hi,
>> > > >
>> > > > I want to update a plugin from 1.8 to QGIS 2.0 and it throws
>> > > > following error:
>> > > >
>> > > > Traceback (most recent call last):
>> > > > File
>> > > >
>> > > >
>> > > > "/home/dassau/.qgis2/python/plugins/weibullanalyse/weibullanalysedialog.py",
>> > > > line 447, in printValue self.showValues() File
>> > > >
>> > > >
>> > > > "/home/dassau/.qgis2/python/plugins/weibullanalyse/weibullanalysedialog.py",
>> > > > line 453, in showValues self.plot() File
>> > > >
>> > > >
>> > > > "/home/dassau/.qgis2/python/plugins/weibullanalyse/weibullanalysedialog.py",
>> > > > line 514, in plot w =
>> > > > float(self.sampleRaster(self.InRastW.currentText(), self.xCoord,
>> > > > self.yCoord))/10 File
>> > > >
>> > > >
>> > > > "/home/dassau/.qgis2/python/plugins/weibullanalyse/weibullanalysedialog.py",
>> > > > line 299, in sampleRaster return self.sampleRaster20(layer, x, y)
>> > > > File
>> > > >
>> > > >
>> > > > "/home/dassau/.qgis2/python/plugins/weibullanalyse/weibullanalysedialog.py",
>> > > > line 284, in sampleRaster20 success, data =
>> > > > layer.dataProvider().identify(QgsPoint(x,y))
>> > > >
>> > > > TypeError:
>> > > > QgsRasterDataProvider.identify(QgsPoint, QgsRaster.IdentifyFormat,
>> > > > QgsRectangle theExtent=QgsRectangle(), int theWidth=0, int
>> > > > theHeight=0): not enough arguments
>> > > >
>> > > > I found at
>> > > > http://hub.qgis.org/wiki/quantum-gis/API_changes_for_version_20 the
>> > > > section QgsRasterDataProvider which should fit. And the Method,
>> > > > where I assume the error occurs should be this
>> > > >
>> > > > # get value at mouse position QGIS <= 1.8 (working for 1.8)
>> > > > def sampleRaster18(self, layer, x, y):
>> > > >    success, data = layer.identify(QgsPoint(x,y))
>> > > >    for band, value in data.items():
>> > > >      return value
>> > > >
>> > > > now what I tried but doesn't work (see error above)
>> > > >
>> > > > # get value at mouse position QGIS >= 2.0 (not working yet :()
>> > > > def sampleRaster20(self, layer, x, y):
>> > > >    success, data = layer.dataProvider().identify(QgsPoint(x,y))
>> > > >    for band, value in data.items():
>> > > >      return value
>> > > >
>> > > > my problem is, that I don't understand how to implement in
>> > > > sampleRaster20 the new method from the API_changes_for_version_20
>> > > > website which says:
>> > > >
>> > > > QMap<int, QVariant> identify( const QgsPoint & thePoint,
>> > > > IdentifyFormat theFormat, const QgsRectangle &theExtent =
>> > > > QgsRectangle(), int theWidth = 0, int theHeight = 0 )
>> > > >
>> > > > can anybody help?
>> > > >
>> > > > Thanks
>> > > >
>> > > > Otto
>> > > > _______________________________________________
>> > > > Qgis-developer mailing list
>> > > > Qgis-developer at lists.osgeo.org
>> > > > http://lists.osgeo.org/mailman/listinfo/qgis-developer
>> > > >
>> >
>> >
>> > --
>> > Geoinformatik Büro Dassau - http://www.gbd-consult.de
>> > FOSSGIS consulting , training , support  and analysis
>> > Ackerstrasse 144c  ,  D - 40233 Düsseldorf  , Germany
>> > Tel: +49-(0)211-47468178 , Mobil: +49-(0)171-4687540
>> >
>> > --
>> > Community Advisor - QGIS Project Steering Committee
>
>
> --
> Geoinformatik Büro Dassau - http://www.gbd-consult.de
> FOSSGIS consulting , training , support  and analysis
> Ackerstrasse 144c  ,  D - 40233 Düsseldorf  , Germany
> Tel: +49-(0)211-47468178 , Mobil: +49-(0)171-4687540
>
> --
> Community Advisor - QGIS Project Steering Committee