[Qgis-user] Re: Raster layer display control from Plugin

[JP Glutting]

No takers? No hints? I have been looking all over the place, and I am stuck.
If it is something absurdly simple, just point me in the right direction.

Any ideas?

Thanks,
JP

On Fri, Sep 3, 2010 at 7:50 AM, JP Glutting <jpglutting at gmail.com> wrote:

> Although here (http://blog.qgis.org/node/94) it seems to indicate that
> SingleBandPseudoColor is a constant:
>
> mypLayer->setColorRampingType(QgsRasterLayer::BLUE_GREEN_RED);
>   mypLayer->setDrawingStyle(QgsRasterLayer::SINGLE_BAND_PSEUDO_COLOR);
>   std::deque myLayerSet;
>
> which is what I was thinking in the first place, and here (
> http://doc.qgis.org/stable/classQgsRasterLayer.html#36796f1a303dac9848ba3dce3e5527dc7b7c9814c053986846b579119d2e5be9 )
> DrawingStyle is described as an enumerator, which seems coherent. I am not
> sure how to do this from Python.
>
> Cheers,
> JP
>
> On Fri, Sep 3, 2010 at 7:43 AM, JP Glutting <jpglutting at gmail.com> wrote:
>
>> Actually, I am not even sure that first part is the way to do it. I tried
>> this:
>>
>>
>>  resultsLayer.setDrawingStyle(QtCore.QString('SingleBandPseudoColor'))
>>         resultsLayer.setCacheImage(None)
>>         resultsLayer.triggerRepaint()
>>
>> (passing the 'SingleBandPseudoColor' style as a string) and it makes the
>> raster invisible. It still shows up black in the Layers Panel, but it
>> doesn't show in the main window until you change the properties manually
>> (and it is Grayscale when you do). It feels like I am pretty close, but I am
>> not sure how to interpret this code from the QGIS documentation:
>>
>> myRasterLayer->setDrawingStyle<http://classQgsRasterLayer.html#3a923f732bedd87d0b920c5552215434>
>> (QgsRasterLayer::SingleBandPseudoColor<http://classQgsRasterLayer.html#36796f1a303dac9848ba3dce3e5527dc7b7c9814c053986846b579119d2e5be9>
>> );
>>
>> (I never learned more than the basics of C++, and that was a long time
>> ago). The source code seems to indicate that the format needs to be passed
>> as a string (of course, when the layer is generated):
>>
>>
>> 00204     QgsRasterLayer <http://classQgsRasterLayer.html>( int dummy,00205                     const QString & baseName = QString(),00206                     const QString & path = QString(),00207                     const QString & providerLib = QString(),00208                     const QStringList & layers = QStringList(),00209                     const QStringList & styles = QStringList(),00210                     const QString & format = QString(),
>>
>> 00211 const QString & crs = QString() );
>>
>> Thanks,
>> JP
>>
>> On Fri, Sep 3, 2010 at 3:04 AM, JP Glutting <jpglutting at gmail.com> wrote:
>>
>>> Hello,
>>>
>>> I am working on a plugin (I mentioned it on the list earlier, but it
>>> isn't relevant to the question I have now). I have the results written to a
>>> raster file, and I need to display it. I am using this code:
>>>
>>>         resultsLayer = qgis.core.QgsRasterLayer(self.query.results_file,
>>> QtCore.QFileInfo(self.query.results_file).baseName())
>>>
>>>  qgis.core.QgsMapLayerRegistry.instance().addMapLayer(resultsLayer)
>>>
>>>
>>> which works fine for opening the file, but I would like to fine-tune the
>>> display so the user doesn't have to reset the properties (in my test exaple
>>> the values are 0 and 1 and the display is essentially all black). I would
>>> like to either display the results in pseudocolor directly, or in grayscale
>>> with the scale stretched to the min and max extent of the raster.
>>>
>>> I tried the psuedocolor with this code:
>>>
>>>
>>>  resultsLayer.setDrawingStyle(qgis.core.QgsRasterLayer.SingleBandPseudoColor)
>>>         resultsLayer.setCacheImage(None)
>>>         resultsLayer.triggerRepaint()
>>>
>>> which doesn't seem to do anything at all, and I am just guessing, really.
>>>
>>> I found a nice tutorial about how to calculate the min and max extent of
>>> a raster and adjust the display here:
>>>
>>> http://linfiniti.com/2010/08/a-simple-qgis-python-tutorial/
>>>
>>> and I tried the following code:
>>>
>>>         band = resultsLayer.bandNumber(resultsLayer.grayBandName())
>>>         extentMin = 0.0
>>>         extentMax = 0.0
>>>         generateLookupTableFlag = False
>>>         extentMin, extentMax =
>>> resultsLayer.computeMinimumMaximumFromLastExtent(band)
>>>         resultsLayer.setMinimumValue(band, extentMin,
>>> generateLookupTableFlag)
>>>         resultsLayer.setMaximumValue(band, extentMax,
>>> generateLookupTableFlag)
>>>         resultsLayer.setStandardDeviations(0.0)
>>>         resultsLayer.setUserDefinedGrayMinimumMaximum( True )
>>>         resultsLayer.setCacheImage(None)
>>>         resultsLayer.triggerRepaint()
>>>
>>> but that fails with the following error:
>>>
>>> Traceback (most recent call last):
>>>   File "/Users//.qgis/python/plugins/mcelite/MCELiteDialog.py", line 361,
>>> in accept
>>>     extentMin, extentMax =
>>> resultsLayer.computeMinimumMaximumFromLastExtent(band)
>>> TypeError: 'float' object is not iterable
>>>
>>>
>>> and I don't understand what the float object is, exactly.
>>>
>>>
>>> Any help or suggestions much appreciated.
>>>
>>>
>>> Cheers,
>>>
>>> JP
>>>
>>
>>
>
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