vtkSplineFilter: Generating mask image.

I have some control points . I am using vtkSplineFilter to uniformly subdivide and generate a closed polyline from these control points. I would like to generate a mask image using the spline filter output, where the region inside the closed contour is filled with white. Please suggest a technique.

You can use vtkPolyDataToImageStencil for this.

However, manual image segmentation has been implemented so many times that I would not recommend spend your time with it. You can instead use/customize/extend segment editors of any of the free, open-source medical image computing applications, such as 3D Slicer or MITK.