# FlyingHeadSlice

VTKExamples/Python/VisualizationAlgorithms/FlyingHeadSlice

### Description

This example generates 2D contour lines on one CT slice through the head. The contours correspond to density values of the tissues and are colored according to density value.

This example is a modification of HeadSlice using vtkFlyingEdges2D for contouring. However there is an option to use vtkContourFilter instead.

Info

See Figure 6-11a in Chapter 6 of the VTK Textbook.

### Code

FlyingHeadSlice.py

    #!/usr/bin/env python

    import vtk

    def main():
        fileName, useContouring = get_program_parameters()
        if useContouring:
            print('Using vtkContourFilter.')
        else:
            print('Using vtkFlyingEdges2D.')

        colors = vtk.vtkNamedColors()

        # Create the RenderWindow, Renderer and Interactor.
        ren1 = vtk.vtkRenderer()
        renWin = vtk.vtkRenderWindow()
        renWin.AddRenderer(ren1)
        iren = vtk.vtkRenderWindowInteractor()
        iren.SetRenderWindow(renWin)

        # Create the pipeline.
        reader = vtk.vtkMetaImageReader()
        reader.SetFileName(fileName)
        reader.Update()

        extractVOI = vtk.vtkExtractVOI()
        extractVOI.SetInputConnection(reader.GetOutputPort())
        extractVOI.SetVOI(0, 255, 0, 255, 45, 45)
        # scalarRange = extractVOI.GetOutput().GetScalarRange()
        scalarRange = [500, 1150]
        # print(scalarRange)

        contour = vtk.vtkContourFilter()
        flyingEdges = vtk.vtkFlyingEdges2D()
        isoMapper = vtk.vtkPolyDataMapper()
        if useContouring:
            contour.SetInputConnection(extractVOI.GetOutputPort())
            contour.GenerateValues(12, scalarRange)
            isoMapper.SetInputConnection(contour.GetOutputPort())
        else:
            flyingEdges.SetInputConnection(extractVOI.GetOutputPort())
            flyingEdges.GenerateValues(12, scalarRange)
            isoMapper.SetInputConnection(flyingEdges.GetOutputPort())

        isoMapper.ScalarVisibilityOn()
        isoMapper.SetScalarRange(scalarRange)

        isoActor = vtk.vtkActor()
        isoActor.SetMapper(isoMapper)
        isoActor.GetProperty().SetColor(colors.GetColor3d("Wheat"))

        outline = vtk.vtkOutlineFilter()
        outline.SetInputConnection(extractVOI.GetOutputPort())

        outlineMapper = vtk.vtkPolyDataMapper()
        outlineMapper.SetInputConnection(outline.GetOutputPort())

        outlineActor = vtk.vtkActor()
        outlineActor.SetMapper(outlineMapper)

        # Add the actors to the renderer, set the background and size.
        ren1.AddActor(outlineActor)
        ren1.AddActor(isoActor)
        ren1.SetBackground(colors.GetColor3d("SlateGray"))
        ren1.ResetCamera()
        ren1.GetActiveCamera().Dolly(1.5)
        ren1.ResetCameraClippingRange()

        renWin.SetSize(640, 480)
        renWin.SetWindowName('Full Head')
        renWin.Render()

        iren.Start()

    def get_program_parameters():
        import argparse
        description = 'Either vtkFlyingEdges2D or vtkContourFilter is used to generate contour lines.'
        epilogue = '''
        Generate 2D contour lines, corresponding to tissue density, on one CT slice through the head.
        The contour lines are colored by the tissue density.
        '''
        parser = argparse.ArgumentParser(description=description, epilog=epilogue,
                                         formatter_class=argparse.RawDescriptionHelpFormatter)
        parser.add_argument('filename', help='FullHead.mhd.')
        parser.add_argument('-useContouring', '--useContouring', action='store_true',
                            help='Use vtkContourFilter instead of vtkFlyingEdges2D.')
        args = parser.parse_args()
        return args.filename, args.useContouring

    if __name__ == '__main__':
        main()