[vtkusers] RGBA to gray in VTK

[Prathamesh Kulkarni]

Hello all,

I am trying to convert an image from RGBA to gray scale so that I can
compare it pixel by pixel with another gray scale image. Following is what I
did:

    vtkSmartPointer<vtkImageMapToColors> gray_from_RGBA_map =
vtkSmartPointer<vtkImageMapToColors>::New();
    grayd_from_RGB_map->SetInput(RGBA_image_data);

    gray_from_RGB_map->SetOutputFormatToLuminance();

    gray_from_RGB_map->Update();

    int channels =
gray_from_RGBA_map->GetOutput()->GetNumberOfScalarComponents();

The variable "channels" is 4 irrespective of whether I include a
vtkImageMapToColors in the pipeline.

Am I doing anything wrong here? What is the best way to do this?


Any help will be highly appreciated.


Prathamesh
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