On 08/09/2010 12:22 PM, Benoit de Cabissole wrote:
Here is the code I'm using:
# tell the layer to use a QgsColorRampShader function
theLayer.setColorShadingAlgorithm( QgsRasterLayer.ColorRampShader )
theLayer.rasterShader().setRasterShaderFunction( QgsColorRampShader() )
# get the raster shader function: should be a QgsColorRampShader
myColorRampShader = theLayer.rasterShader().rasterShaderFunction()
# set parameter for the QgsColorRampShader function
myColorRampShader.setColorRampItemList( theTBL )
myColorRampShader.setMaximumColorCacheSize( nColo )
myColorRampShader.setColorRampType( myColorRampShader.DISCRETE )
# feed my custom QgsColorRampShader back to the raster
theLayer.setRasterShaderFunction( myColorRampShader )
It does not produce an error but raster does not change to the given
colormap.
Benoit,
With Martin's recent updates you can remove a couple of lines,
---theLayer.rasterShader().setRasterShaderFunction( QgsColorRampShader()
) can be removed, setColorShadingAlgorithm() already creates a new
shader instance and theLayer.rasterShader().rasterShaderFunction() new
returns the actual class not the base class, thanks Martin!
---theLayer.setRasterShaderFunction( myColorRampShader ) is also not
necessary, because you are already working with the actual shader (i.e.,
myColorRampShader ). This will also cause a crash/segfault because the
setRasterShaderFunction() now is deleting the existing function and
replacing it with the new, however, in this case it is deleting itself.
MARTIN: This was why QgsRasterLayer managed deleting the functions and
checked to see if the QgsRasterShaderFunction was user defined. I saw
too many possibilities for crashes if the shader itself managed the
deleting of functions. This case illustrates on instance of that problem.
I suspect you are not seeing your changes because the draying style is
not set correctly. For example, if you load a gray scale image and then
apply a color map using the above code, you will still have to set the
drawing style to a type that will use the shader as apposed to a
contrast enhancement.
>>theLayer.setDrawingStyle( QgsRasterLayer.SingleBandPseudoColor )
>>theLayer.triggerRepaint()
The same would apply for multi band images:
>>theLayer.setDrawingStyle( QgsRasterLayer.MultiBandSingleBandPseudoColor )
If it would help I could give you a complete example with sample data,
but it would have to wait until the end of the week.
-pete
--
====================================
Peter J. Ersts, Software Developer
American Museum of Natural History
Center for Biodiversity and Conservation
Central Park West at 79th Street
New York, New York 10024
Web: http://biodiversityinformatics.amnh.org
Web: http://cbc.amnh.org
Open Source,
...evolving through community cooperation to change the world bit by bit
Quantum GIS Raster Development Team.
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