[Insight-users] GetPixel problem

[C. Aaron Cois]

Looks to me like you didn't call Update() on the reader to actually read 
in the image. Add the line

reader->Update();

right after

image = reader->GetOutput();

and you should be fine.

-Aaron

Robert Maroon wrote:

>Hi all,
>
>I am currently writing an application where I input a
>100x100x100 3D volume and I am simply trying to get
>the value at one pixel and do a cout to see the value.
>
>
>However, as soon as I call GetPixel, I get a
>segmentation fault. The pixel coordinates I pass are
>definitely within the bounds of the volume so I can't
>see what the problem is.
>
>I've included the code below (it is a modification of
>the image3.cxx example from Examples/Data
>Representation/Image), with the problematic line of
>code commented.
>
>Thanks!
>
>
>#include "itkImage.h"
>#include "itkImageFileReader.h"
>#include <iostream>
>using namespace std;
>
>int main(int , char ** argv)
>{
>  int i, j, k;
>  typedef unsigned char	         PixelType;
>  const unsigned int             Dimension = 3;
>
>  // First the image type should be declared
>  typedef itk::Image< PixelType, Dimension >
>ImageType;
>
>  // Then the image object can be created
>  ImageType::Pointer image = ImageType::New();
>
>  // Define typedefs for the readers and writers
>  typedef itk::ImageFileReader< ImageType >
>ReaderType;
>
>  // Initialize pointers for the readers and writers
>  ReaderType::Pointer reader = ReaderType::New();
>
>  reader->SetFileName( argv[0] );
>
>  // The image region should be initialized
>  ImageType::IndexType start;
>  ImageType::SizeType  size;
>
>  size[0]  = 100;  // size along X
>  size[1]  = 100;  // size along Y
>  size[2]  = 100;  // size along Z
>
>  start[0] =   0;  // first index on X
>  start[1] =   0;  // first index on Y
>  start[2] =   0;  // first index on Z
>
>  ImageType::RegionType region;
>  region.SetSize( size );
>  region.SetIndex( start );
>
>  // Pixel data is allocated
>  image->SetRegions( region );
>  image->Allocate();
>  image = reader->GetOutput();
>
>  ImageType::IndexType pixelIndex;
>  pixelIndex[0] = 50;
>  pixelIndex[1] = 50;
>  pixelIndex[2] = 9;
>
>  /* CRASHES ON THIS LINE WITH A SEGMENTATION FAULT */
>  ImageType::PixelType  pixelValue = 
>                        image->GetPixel( pixelIndex );
>  cout<<"Pixel Value is:"<<pixelValue<<"\n";
>
>  return 0;
>
>}
>
>
>	
>		
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