[Insight-users] How to restrict a filter to a region

[Elena Pavlovskaia]

Hello!

I want to apply a filter to a sub-region in my image.

Looking into comments in the header files I though I had to call
SetRequestedRegion before executing the filter.

I tried calling SetRequestedRegion with both input and output images
of the filter, but the filter seemed to be always applied to the whole
image.
I tried doing it with a) SignedDanielssonDistanceMapImageFilter;
b) DiscreteGaussianImageFilter.

Can somebody advise on how I could restrict a filter execution to a region?
I am mostly interested with restricting the DiscreteGaussianImageFilter.

I pasted below the code where I am trying to restrict the
SignedDanielssonDistanceMapImageFilter to a sub-region.

I run it with the following parameters:
"InitialImage.png" "SmoothedImage.png" 4 4
The first two parameters stand for the names of the output images:
before smoothing and after smoothing.
The last two parameters are the filter parameters.

I attached the output of my program execution. The SmoothedImage.png looks
like
if the smoothing filter were applied to the whole image.

Thank you!

Elena

------------- MY CODE --------------

#if defined(_MSC_VER)
#pragma warning ( disable : 4786 )
#endif

#ifdef __BORLANDC__
#define ITK_LEAN_AND_MEAN
#endif


#include "itkImage.h"
#include "itkImageRegionIteratorWithIndex.h"
#include "itkImageFileWriter.h"
#include "itkCastImageFilter.h"

#include "itkDiscreteGaussianImageFilter.h"


int main( int argc, char * argv[] )
	{
	if( argc < 5 ) 
		{ 
		std::cerr << "Usage: " << std::endl;
		std::cerr << argv[0] << "  InitialImageFile
SmoothedImageFile variance  maxKernelWidth " << std::endl;
		return EXIT_FAILURE;
		}

	typedef    float    InputPixelType;
	typedef    float    OutputPixelType;

	typedef itk::Image< InputPixelType,  2 >   InputImageType;
	typedef itk::Image< OutputPixelType, 2 >   OutputImageType;

	typedef unsigned char WritePixelType;
	typedef itk::Image< WritePixelType, 2 > WriteImageType;

	typedef itk::CastImageFilter< 
		OutputImageType, WriteImageType > CastFilterType;
	CastFilterType::Pointer caster = CastFilterType::New();

	typedef itk::ImageFileWriter< WriteImageType >  WriterType;

	WriterType::Pointer writer1 = WriterType::New();
	writer1->SetFileName( argv[1] );
	WriterType::Pointer writer2 = WriterType::New();
	writer2->SetFileName( argv[2] );

	// Create input image
	InputImageType::Pointer image = InputImageType::New();  

	InputImageType::IndexType start;

	start[0] =   0;  // first index on X
	start[1] =   0;  // first index on Y

	const unsigned int length = 50;
	InputImageType::SizeType  size;

	size[0]  = length;  // size along X
	size[1]  = length;  // size along Y

	InputImageType::RegionType region;

	region.SetSize( size );
	region.SetIndex( start );

	image->SetRegions( region );
	image->Allocate();

	// Fill in the top/left triangle with 0, and the right/bottom
triangle with 255:

	typedef  itk::ImageRegionIteratorWithIndex<InputImageType>
IteratorType;
	IteratorType it( image, region );

	InputPixelType subtract = length - 1;

	it.GoToBegin();
	while( !it.IsAtEnd() )
		{
		InputImageType::IndexType index = it.GetIndex();
		InputPixelType value = index[0] + index[1] - subtract;
		if( value > 0 )
			{
			value = 255.0;
			}
		else
			{
			value = 0.0;
			}

		it.Set( value );
		++it;
		}

	// Write down our initial image:
	caster->SetInput( image );
	caster->Modified();
	writer1->SetInput( caster->GetOutput() );
	writer1->Update();

	// Init a smoothing filter:
	typedef itk::DiscreteGaussianImageFilter<
		InputImageType, OutputImageType >  FilterType;

	FilterType::Pointer filter = FilterType::New();
	filter->SetInput( image );

	const double gaussianVariance = atof( argv[3] );
	const unsigned int maxKernelWidth = atoi( argv[4] );

	filter->SetVariance( gaussianVariance );
	filter->SetMaximumKernelWidth( maxKernelWidth );

	// Create a regionOut with the sizes = 1/2 of the whole image
	// and set it as requested region for in and out images of the
smoothing filter:

	OutputImageType::Pointer smoothImage = filter->GetOutput();

	OutputImageType::RegionType regionOut = region;
	OutputImageType::RegionType::SizeType sizeOut;

	sizeOut[0] = size[0]/2;
	sizeOut[1] = size[1]/2;

	regionOut.SetSize( sizeOut );
	smoothImage->SetRegions( region );
	smoothImage->Allocate();

	image->SetRequestedRegion( regionOut );
	smoothImage->SetRequestedRegion( regionOut );

	// Execute the filter:
	filter->Update();

	// Write down the result:

	caster->SetInput( smoothImage );
	caster->Modified();
	writer2->SetInput( caster->GetOutput() );
	writer2->Update();

	return EXIT_SUCCESS;
	}
-------------- next part --------------
A non-text attachment was scrubbed...
Name: InitialImage.png
Type: image/png
Size: 268 bytes
Desc: not available
Url : http://public.kitware.com/pipermail/insight-users/attachments/20070416/32da7147/InitialImage.png
-------------- next part --------------
A non-text attachment was scrubbed...
Name: SmoothedImage.png
Type: image/png
Size: 344 bytes
Desc: not available
Url : http://public.kitware.com/pipermail/insight-users/attachments/20070416/32da7147/SmoothedImage.png