[vtkusers] vtkImageBlend output alpha

[Mike Withascarf]

Hi, I'm using vtkImageBlend to blend two vtkImageMapToColors. Right now if I change the opacity map of the first vtkImageMapToColors (via lookup table), it adjusts the entire alpha of the output (so for example hiding the first one hides both of them). Is there a way to prevent vtkImageBlend from assigning the opacity of the first element to the output? I've tried using the "compound" blending mode in case that would help, but the screen is blank then. Any help would be great!
This is a simplified version of the code I'm using:
vtkSmartPointer<vtkImageMapToColors> imapper1 = vtkSmartPointer<vtkImageMapToColors>::New();imapper1->SetLookupTable(lut1);imapper1->PassAlphaToOutputOn();imapper1->SetInputData(image1);imapper1->Update();
vtkSmartPointer<vtkImageMapToColors> imapper2 = vtkSmartPointer<vtkImageMapToColors>::New();imapper2->SetLookupTable(lut2);imapper2->PassAlphaToOutputOn();imapper2->SetInputData(image2);imapper2->Update();
vtkSmartPointer<vtkImageBlend> blend = vtkSmartPointer<vtkImageBlend>::New();blend->AddInputConnection(imapper1->GetOutputPort());blend->SetOpacity(0, 1.0);blend->AddInputConnection(imapper2->GetOutputPort());blend->SetOpacity(1, 1.0);
// If I now render and adjust lut1, it affects the output of blend so the imapper2 image gets affected
Mike
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