[Qgis-user] Raster layer display control from Plugin

[JP Glutting]

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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