[vtkusers] A question about displaying Image using VTK

[Cory Quammen]

Instead of using a vtkColorTransferFunction, try using
a vtkDiscretizableColorTransferFunction and setting the opacity function
via SetScalarOpacityFunction(), e.g.

vtkSmartPointer<vtkDiscretizableColorTransferFunction >
colorTransferFunction =
vtkSmartPointer<vtkDiscretizableColorTransferFunction >::New();
colorTransferFunction->AddRGBPoint(0,0,0.5,0);
colorTransferFunction->AddRGBPoint(60,1,0,0);
colorTransferFunction->AddRGBPoint(255,0.8,0.8,0.8);
colorTransferFunction->SetScalarOpacityFunction(opacityTransferFunction);

then enable opacity mapping with

colorTransferFunction->EnableOpacityMappingOn();

HTH,
Cory

On Thu, Jul 9, 2015 at 9:51 AM, 15891495523 at 126.com <15891495523 at 126.com>
wrote:

> Dear all
>
>     I feel confused when display a CT image using VTK. How can I make
> those black and gray part in the following picture invisible ?
>     The key part of my code is :
>
> vtkSmartPointer<vtkPiecewiseFunction> opacityTransferFunction =
> vtkSmartPointer<vtkPiecewiseFunction>::New();
>         opacityTransferFunction->AddPoint(0,1200);
>         opacityTransferFunction->AddPoint(1200,0.4);
>         opacityTransferFunction->AddPoint(2000,0.2);
>
>         vtkSmartPointer<vtkColorTransferFunction> colorTransferFunction =
> vtkSmartPointer<vtkColorTransferFunction>::New();
>         colorTransferFunction->AddRGBPoint(0,0,0.5,0);
>         colorTransferFunction->AddRGBPoint(60,1,0,0);
>         colorTransferFunction->AddRGBPoint(255,0.8,0.8,0.8);
>
>
> Thank you in advanced!
>
> ZhangQiang
>
>
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-- 
Cory Quammen
R&D Engineer
Kitware, Inc.
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