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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Dear All,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am trying to look through the itkGradientMagnitudeRecursiveGaussianImageFilter to figure out the pipeline of this filter to visualize the computation process of image gradient calculation from a CT volume dataset using this filter. However, the source code of this filter makes me confused about the pipeline in this filter due to my limited programming skill.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This filter consists of two major steps as far as I know: 1) image smoothing using itkRecursiveGaussianImageFilter, and 2) image gradient calculation using a finite difference method (Does anybody know what formula was used for the finite difference method? I checked the source code but could not get it). <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>For step 1, I wrote a code to get the smoothed image. But I am not sure whether my code would get the same smoothed image as itkGradientMagnitudeRecursiveGaussianImageFilter or not. Please check my code and point out which part I missed or is not correct. Thank you very much!<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun;color:green'>// Setup types<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:blue'>typedef</span> itk::Image< <span style='color:blue'>float</span>, 3 > FloatImageType;<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:blue'>typedef</span> itk::Image< <span style='color:blue'>unsigned</span> <span style='color:blue'>char</span>, 3 > UnsignedCharImageType;<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:blue'>typedef</span> itk::ImageFileReader< FloatImageType > readerType;<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:blue'>typedef</span> itk::RecursiveGaussianImageFilter<<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> FloatImageType, FloatImageType > filterType;<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:green'>// Create and setup a reader<o:p></o:p></span></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> readerType::Pointer reader = readerType::New();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> reader->SetFileName( <span style='color:#A31515'>"D:/Hybrid Method/Hybrid/LEJ/Diffusion_filter/3D.dcm"</span> );<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:green'>// Create and setup a gaussian filter<o:p></o:p></span></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> filterType::Pointer m_DerivativeFilter = filterType::New();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_DerivativeFilter->SetInput( reader->GetOutput() );<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:green'>//m_DerivativeFilter->SetDirection(1); // "x" axis<o:p></o:p></span></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_DerivativeFilter->SetFirstOrder();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_DerivativeFilter->SetSigma(1.3);<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_DerivativeFilter->SetNormalizeAcrossScale(<span style='color:blue'>true</span>);<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_DerivativeFilter->ReleaseDataFlagOn();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> filterType::Pointer m_SmoothingFilters[2]; <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:blue'>for</span>( <span style='color:blue'>unsigned</span> <span style='color:blue'>int</span> i = 0; i< 2; i++ )<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> {<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_SmoothingFilters[ i ] = filterType::New();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_SmoothingFilters[ i ]->SetZeroOrder();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_SmoothingFilters[ i ]->SetNormalizeAcrossScale( <span style='color:blue'>true</span> ); <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_SmoothingFilters[ i ]->SetSigma( 1.3 );<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> }<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_SmoothingFilters[0]->SetInput( m_DerivativeFilter->GetOutput() );<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:blue'>for</span>( <span style='color:blue'>unsigned</span> <span style='color:blue'>int</span> i = 1; i< 2; i++ )<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> {<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> m_SmoothingFilters[ i ]->SetInput( m_SmoothingFilters[i-1]->GetOutput() );<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> }<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:blue'>typedef</span> itk::CastImageFilter< FloatImageType, UnsignedCharImageType ><o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> CastFilterType;<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> CastFilterType::Pointer caster1 = CastFilterType::New();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> caster1->SetInput( m_SmoothingFilters[1]->GetOutput() ); <span style='color:green'><o:p></o:p></span></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> <span style='color:blue'>typedef</span> itk::ImageFileWriter< UnsignedCharImageType > WriterType;<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> WriterType::Pointer writer1 = WriterType::New();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> writer1->SetFileName( <span style='color:#A31515'>"RecusiveGaussian.dcm"</span> );<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> writer1->SetInput(caster1->GetOutput());<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'> writer1->Update();<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal style='text-indent:9.0pt'><span style='font-size:9.0pt;font-family:NSimSun;color:blue'>return</span><span style='font-size:9.0pt;font-family:NSimSun'> EXIT_SUCCESS;<o:p></o:p></span></p><p class=MsoNormal style='text-indent:9.0pt'><span style='font-size:9.0pt;font-family:NSimSun'><o:p> </o:p></span></p><p class=MsoNormal>Best regards,<o:p></o:p></p><p class=MsoNormal>Xiaopeng<o:p></o:p></p></div></body></html>