IdealHighPass
VTKExamples/Python/ImageProcessing/IdealHighPass
Description¶
Low-pass and high-pass filtering become trivial in the frequency domain. A portion of the pixels are simply masked or attenuated. This example shows a high pass Butterworth filter that attenuates the frequency domain image with the function out(i, j) = 1 / (1 + pow(CutOff/Freq(i,j), 2*Order))
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See (Cxx)
Code¶
IdealHighPass.py
#!/usr/bin/env python """ """ import vtk def main(): colors = vtk.vtkNamedColors() fileName = get_program_parameters() # Read the image. readerFactory = vtk.vtkImageReader2Factory() reader = readerFactory.CreateImageReader2(fileName) reader.SetFileName(fileName) reader.Update() fft = vtk.vtkImageFFT() fft.SetInputConnection(reader.GetOutputPort()) idealHighPass = vtk.vtkImageIdealHighPass() idealHighPass.SetInputConnection(fft.GetOutputPort()) idealHighPass.SetXCutOff(0.1) idealHighPass.SetYCutOff(0.1) idealRfft = vtk.vtkImageRFFT() idealRfft.SetInputConnection(idealHighPass.GetOutputPort()) idealReal = vtk.vtkImageExtractComponents() idealReal.SetInputConnection(idealRfft.GetOutputPort()) idealReal.SetComponents(0) butterworthHighPass = vtk.vtkImageButterworthHighPass() butterworthHighPass.SetInputConnection(fft.GetOutputPort()) butterworthHighPass.SetXCutOff(0.1) butterworthHighPass.SetYCutOff(0.1) butterworthRfft = vtk.vtkImageRFFT() butterworthRfft.SetInputConnection(butterworthHighPass.GetOutputPort()) butterworthReal = vtk.vtkImageExtractComponents() butterworthReal.SetInputConnection(butterworthRfft.GetOutputPort()) butterworthReal.SetComponents(0) # Create the actors. idealColor = vtk.vtkImageMapToWindowLevelColors() idealColor.SetWindow(500) idealColor.SetLevel(0) idealColor.SetInputConnection(idealReal.GetOutputPort()) idealActor = vtk.vtkImageActor() idealActor.GetMapper().SetInputConnection(idealColor.GetOutputPort()) idealActor.GetProperty().SetInterpolationTypeToNearest() butterworthColor = vtk.vtkImageMapToWindowLevelColors() butterworthColor.SetWindow(500) butterworthColor.SetLevel(0) butterworthColor.SetInputConnection(butterworthReal.GetOutputPort()) butterworthActor = vtk.vtkImageActor() butterworthActor.GetMapper().SetInputConnection(butterworthColor.GetOutputPort()) butterworthActor.GetProperty().SetInterpolationTypeToNearest() # Setup the renderers. idealRenderer = vtk.vtkRenderer() idealRenderer.SetViewport(0.0, 0.0, 0.5, 1.0) idealRenderer.AddActor(idealActor) idealRenderer.ResetCamera() idealRenderer.SetBackground(colors.GetColor3d("SlateGray")) butterworthRenderer = vtk.vtkRenderer() butterworthRenderer.SetViewport(0.5, 0.0, 1.0, 1.0) butterworthRenderer.AddActor(butterworthActor) butterworthRenderer.SetActiveCamera(idealRenderer.GetActiveCamera()) butterworthRenderer.SetBackground(colors.GetColor3d("LightSlateGray")) renderWindow = vtk.vtkRenderWindow() renderWindow.SetSize(600, 300) renderWindow.AddRenderer(idealRenderer) renderWindow.AddRenderer(butterworthRenderer) renderWindowInteractor = vtk.vtkRenderWindowInteractor() style = vtk.vtkInteractorStyleImage() renderWindowInteractor.SetInteractorStyle(style) renderWindowInteractor.SetRenderWindow(renderWindow) idealRenderer.GetActiveCamera().Dolly(1.4) idealRenderer.ResetCameraClippingRange() renderWindowInteractor.Initialize() renderWindowInteractor.Start() def get_program_parameters(): import argparse description = 'This figure shows two high-pass filters in the frequency domain.' epilogue = ''' The Butterworth high-pass filter has a gradual attenuation that avoids ringing produced by the ideal high-pass filter with an abrupt transition. ''' parser = argparse.ArgumentParser(description=description, epilog=epilogue, formatter_class=argparse.RawDescriptionHelpFormatter) parser.add_argument('filename', help='fullhead15.png.') args = parser.parse_args() return args.filename if __name__ == '__main__': main()