[vtkusers] [vtk-developers] Bug in vtkImageMapToColors

[Nicolas Rannou]

Hi David, 

Thanks for the clarification.
Which is the best practice to get the scalar range of each component then?


On May 6, 2011, at 5:53 PM, David Gobbi wrote:

> Hi Nicolas,
> 
> The GetScalarRange() method computes the scalar range of the first component.
> 
> - David
> 
> 
> On Fri, May 6, 2011 at 3:00 PM, Nicolas Rannou
> <nicolas_rannou at hms.harvard.edu> wrote:
>> Hello,
>> 
>> I'm experiencing a strange behavior in VTK which might be a bug.
>> It took me a while to locate the issue:
>> 
>> if I create a LUT with a NULL red component:
>>   iRed = 0;
>>   iGreen = 255;
>>   iBlue = 255;
>>   iAlpha = 255;
>>   double iRange[2] = {0, 255};
>> 
>>   vtkSmartPointer<vtkLookupTable> lut =
>>       vtkSmartPointer<vtkLookupTable>::New();
>>   double* HSV = vtkMath::RGBToHSV(iRed,iGreen,iBlue);
>>   lut->SetAlpha(iAlpha);
>>   lut->SetHueRange(HSV[0], HSV[0]);
>>   lut->SetSaturationRange(1, 1);
>>   lut->SetValueRange(0, 1);
>>   lut->SetRange(iRange);
>>   lut->Build();
>> 
>> I color my image with this LUT:
>> 
>>   vtkSmartPointer<vtkImageMapToColors> coloredImage =
>>       vtkSmartPointer<vtkImageMapToColors>::New();
>>   coloredImage->SetLookupTable(iLUT);
>>   coloredImage->SetInput( iImage );
>>   coloredImage->PassAlphaToOutputOff();
>>   coloredImage->SetOutputFormatToRGB();
>>   coloredImage->Update();
>> 
>> then:
>>   double* range = coloredImage->GetOutput()->GetScalarRange();
>> returns [0,0].
>> then everything I do with this image is messed up...
>> 
>> If iRed != 0, the scalar range of the "coloredImage" will be correct then my
>> pipeline is working.
>> 
>> Am I doing something wrong?
>> 
>> Thanks,
>> 
>> Nicolas
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