[Insight-users] separate interlaced frames

[Alex. GOUAILLARD]

hi all,

I am trying to separate two interlaced frames from a 1024*1024 image.

I modified the code from Examples/Iterators/ImageLinearIteratorWithIndex.cxx
to copy only one line out of two in the output image.
It works.

But when I try to modify the spacing of the output image to be half the 
one of the input, I have a memory access error thrown by the writer. I 
must be missing something very simple, does anyone see it?

alex

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

#include "itkImage.h"
#include "itkRGBPixel.h"
#include "itkImageLinearConstIteratorWithIndex.h"
#include "itkImageLinearIteratorWithIndex.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"

int main( int argc, char *argv[] )
{
   // Verify the number of parameters on the command line.
   if ( argc < 3 )
     {
     std::cerr << "Missing parameters. " << std::endl;
     std::cerr << "Usage: " << std::endl;
     std::cerr << argv[0]
               << " inputImageFile outputImageFile"
               << std::endl;
     return -1;
     }

   // 2 to get one slice
   // 3 to get on time point
   // 4 if I get crazy enough one day to make one big file
   const unsigned int Dimension = 2;

   typedef itk::RGBPixel< unsigned char > RGBPixelType;
   typedef itk::Image< RGBPixelType, Dimension >  ImageType;

   typedef itk::ImageLinearIteratorWithIndex< ImageType > IteratorType;
   typedef itk::ImageLinearConstIteratorWithIndex< ImageType > 
ConstIteratorType;

   typedef itk::ImageFileReader< ImageType > ReaderType;
   typedef itk::ImageFileWriter< ImageType > WriterType;

   ImageType::ConstPointer inputImage;
   ReaderType::Pointer reader = ReaderType::New();
   reader->SetFileName( argv[1] );
   try
     {
     reader->Update();
     inputImage = reader->GetOutput();
     }
   catch ( itk::ExceptionObject &err)
     {
     std::cout << "ExceptionObject caught a !" << std::endl;
     std::cout << err << std::endl;
     return -1;
     }

   ImageType::Pointer outputImage1 = ImageType::New();
   ImageType::RegionType Region =  inputImage->GetRequestedRegion();
   ImageType::SizeType size = Region.GetSize( );
   // size[1] = size[1] / 2; // only y: one line out of two
   Region.SetSize( size );

   outputImage1->SetRegions( Region );
   outputImage1->CopyInformation( inputImage );
   outputImage1->Allocate();
   ImageType::SpacingType spacing = inputImage->GetSpacing( );
   //spacing[1] *= 2;
   outputImage1->SetSpacing( spacing );

   ConstIteratorType inputIt( inputImage, 
inputImage->GetRequestedRegion() );
   IteratorType outputIt( outputImage1, inputImage->GetRequestedRegion() );

   inputIt.SetDirection(0);
   outputIt.SetDirection(0);

   for ( inputIt.GoToBegin(),  outputIt.GoToBegin(); ! inputIt.IsAtEnd();
         outputIt.NextLine(),  inputIt.NextLine())
     {
     inputIt.GoToBeginOfLine();
     outputIt.GoToEndOfLine();
     --outputIt;
     while ( ! inputIt.IsAtEndOfLine() )
       {
       outputIt.Set( inputIt.Get() );
       ++inputIt;
       --outputIt;
       }
     // skip one line
     inputIt.NextLine();
     }

   WriterType::Pointer writer = WriterType::New();
   writer->SetFileName( argv[2] );
   writer->SetInput(outputImage1);
   try
     {
     writer->Update();
     }
   catch ( itk::ExceptionObject &err)
     {
     std::cout << "ExceptionObject caught !" << std::endl;
     std::cout << err << std::endl;
     return -1;
     }

   return 0;
}