[Qgis-developer] How to color a raster with a color table with values From - To?

[Etienne Tourigny]

Hi

sorry if I have misled you, the code I was quoting is in 1.9 (dev
version). Have a look at the code in 1.9, it should probably work with
1.8 but might require some changes.

https://github.com/qgis/Quantum-GIS/blob/master/tests/src/core/testqgsrasterlayer.cpp

//items to imitate old pseudo color renderer
  QList<QgsColorRampShader::ColorRampItem> colorRampItems;
  QgsColorRampShader::ColorRampItem firstItem;
  firstItem.value = 0.0;
  firstItem.color = QColor( "#0000ff" );
  colorRampItems.append( firstItem );
[...]
  colorRampShader->setColorRampItemList( colorRampItems );


Etienne

On Mon, Aug 13, 2012 at 8:12 AM, SupportLists <supportlists at qlands.com> wrote:
> Hi,
>
> I am using 1.8.0 but tests/src/core/testqgsrasterlayer.cpp is defined as:
>
> void TestQgsRasterLayer::pseudoColor()
> {
>   mpRasterLayer->setDrawingStyle( QgsRasterLayer::SingleBandPseudoColor );
>   mpRasterLayer->setColorShadingAlgorithm( QgsRasterLayer::PseudoColorShader
> );
>   mpRasterLayer->setContrastEnhancementAlgorithm(
>     QgsContrastEnhancement::StretchToMinimumMaximum, false );
>   mpRasterLayer->setMinimumValue( mpRasterLayer->grayBandName(), 0.0, false
> );
>   mpRasterLayer->setMaximumValue( mpRasterLayer->grayBandName(), 10.0 );
>   mpMapRenderer->setExtent( mpRasterLayer->extent() );
>   QVERIFY( render( "raster_pseudo" ) );
> }
>
> I cannot locate the code using ColorRampItem.
>
> Many thanks,
> Carlos.
>
>
> On 08/08/2012 08:07 PM, Etienne Tourigny wrote:
>>
>> Hi,
>>
>> which version of the api are you using? If you are using the
>> development version (1.9), there is support for more flexible color
>> ramps with rasters, using QgsVectorColorRampV2. Beware, however, that
>> the api is going to suffer some changes in the near future. There are
>> various recent threads on this subject in this mailing list.
>>
>> Another option (and the only available if using 1.8) is to follow the
>> approach used in the rasterlayer test in
>> tests/src/core/testqgsrasterlayer.cpp .
>> TestQgsRasterLayer::pseudoColor() uses a ColorRampItem vector and
>> calls colorRampShader->setColorRampItemList(items)
>>
>> Etienne
>>
>> On Wed, Aug 8, 2012 at 3:42 AM, SupportLists <supportlists at qlands.com>
>> wrote:
>>>
>>> Hi,
>>>
>>> I am using QGIS API to develop a custom application. Currently I'm using
>>> QgsRasterLayer::PalettedColor + QgsRasterLayer::ColorRampShader  +
>>> QgsColorRampShader::ColorRampItem to render a raster using a specific
>>> color
>>> map.
>>>
>>> Now, I need to render the raster with a colormap using value From - To
>>> however, ColorRampItem struct only accepts one value. Is there another
>>> way
>>> around? Or, its it possible to create user defined DrawingStyles and
>>> ColorShadingAlgorithms? If so how?
>>>
>>> Any help is very much appreciated.
>>>
>>> Regards,
>>> Carlos.
>>> _______________________________________________
>>> Qgis-developer mailing list
>>> Qgis-developer at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/qgis-developer
>
>
>