How to change vtkImageReslice background color

Hello,

When I create a vtkImageReslice and rotate it using the SetResliceAxes function, I get a gray background.

Is there a way to change the gray background to black?

    imageReslice->SetBackgroundColor(0.0, 0.0, 0.0, 0.0);
    imageReslice->AutoCropOutputOn();
    imageReslice->SetOptimization(1);
    imageReslice->SetOutputDimensionality(2);	
    imageReslice->SetInterpolationModeToLinear();	

    imageReslice->SetResliceAxes(matrix);

I solved it by referring to the link below.
(Problem with ImageReslice)

SetBackgroundLevel(-1000.0);