[Insight-users] FFTImageFilter

[Ming Chao]

float

On Wed, Aug 4, 2010 at 2:38 PM, Markus Neuner <neuner.markus at gmx.net> wrote:

>  What is the pixel type of "ImageType"?
>
>
> On 04.08.2010 21:11, Ming Chao wrote:
>
> I checked the complex image FFT created from the input image was fine. Also
> I checked the real and imaginary parts in floating point format,
> respectively. They both are fine. The problem started to happen when
> rescaling the real/imaginary image into an interger-type image. Here is part
> of the rescaling code:
>
>    typedef unsigned char WritePixelType;
>   typedef itk::Image< WritePixelType, Dimension > WriteImageType;
>
>   typedef itk::RescaleIntensityImageFilter<ImageType, WriteImageType >
> RescaleFilterType;
>
>    RescaleFilterType::Pointer intensityRescaler =
> RescaleFilterType::New();
>   intensityRescaler->SetOutputMinimum(  0  );
>   intensityRescaler->SetOutputMaximum( 255 );
>
>   intensityRescaler->SetInput( realFilter->GetOutput() );
>
>    typedef itk::ImageFileWriter< WriteImageType > WriterType;
>   WriterType::Pointer writer = WriterType::New();
>   writer->SetFileName( argv[2] );
>   writer->SetInput( intensityRescaler->GetOutput() );
>
>    try
>     {
>  writer->Update();
>     }
>   catch( itk::ExceptionObject & excp )
>     {
>  std::cerr << "Error writing the real image: " << std::endl;
>  std::cerr << excp << std::endl;
>  return EXIT_FAILURE;
>     }
>
>    typedef itk::ImageRegionConstIterator< WriteImageType >
> ConstIteratorType;
>   WriteImageType::Pointer RealImage = intensityRescaler->GetOutput();
>   ConstIteratorType in( RealImage, RealImage->GetRequestedRegion() );
>
>   for ( in.GoToBegin(); !in.IsAtEnd(); ++in )
>   {
>   std::cout << in.Get() << std::endl;
>   }
>
>
>  From the output I got all zeros....Apparently something wrong with the
> rescaler. Could anybody take a look? Thanks very much,
>
>  Ming
>
>
> On Wed, Aug 4, 2010 at 9:35 AM, Ming Chao <mingchao2005 at gmail.com> wrote:
>
>> I tried to run FFTImageFilter.cxx to do an FFT of an image. The input
>> image is a 512x512, 24 bit thoracic CT image in jpg format. The output of
>> the example cxx code are the real and imaginary parts of FFT of the input
>> image. However, when I look at the two output images, they are just
>> uniformly grey/black, depending on
>>
>>    intensityRescaler->SetOutputMinimum(  0  );
>>   intensityRescaler->SetOutputMaximum( 255 );
>>
>>  in the code. What did I do wrong? Many thanks,
>>
>>  Ming
>>
>>
>
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