Examples/DataRepresentation/Image/Image3.cxx

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// Software Guide : BeginLatex
//
// This example illustrates the use of the \code{SetPixel()} and
// \code{GetPixel()} methods.  These two methods provide direct access to the
// pixel data contained in the image. Note that these two methods are
// relatively slow and should not be used in situations where
// high-performance access is required. Image iterators are the appropriate
// mechanism to efficiently access image pixel data. (See
// Chapter~\ref{sec:ImageIteratorsChapter} on page
// \pageref{sec:ImageIteratorsChapter} for information about image
// iterators.)
//
// Software Guide : EndLatex


#include "itkImage.h"

int main(int, char *[])
{
  // First the image type should be declared
  using ImageType = itk::Image< unsigned short, 3 >;

  // Then the image object can be created
  ImageType::Pointer image = ImageType::New();

  // The image region should be initialized
  const ImageType::SizeType  size  = {{ 200, 200, 200}}; //Size along {X,Y,Z}
  const ImageType::IndexType start = {{ 0, 0, 0 }}; // First index on {X,Y,Z}

  ImageType::RegionType region;
  region.SetSize( size );
  region.SetIndex( start );

  // Pixel data is allocated
  image->SetRegions( region );
  image->Allocate(true); // initialize buffer to zero


  // Software Guide : BeginLatex
  //
  // The individual position of a pixel inside the image is identified by a
  // unique index. An index is an array of integers that defines the position
  // of the pixel along each dimension of the image. The \code{IndexType}
  // is automatically defined by the image and can be accessed using the
  // scope operator \doxygen{Index}. The length of the array will match
  // the dimensions of the associated image.
  //
  // The following code illustrates the declaration of an index variable and
  // the assignment of values to each of its components. Please note that
  // no \code{SmartPointer} is used to access the \code{Index}. This is because
  // \code{Index} is a lightweight object that is not intended to be shared
  // between objects. It is more efficient to produce multiple copies of
  // these small objects than to share them using the SmartPointer
  // mechanism.
  //
  // The following lines declare an instance of the index type and initialize
  // its content in order to associate it with a pixel position in the image.
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  const ImageType::IndexType pixelIndex = {{27,29,37}}; // Position of {X,Y,Z}
  // Software Guide : EndCodeSnippet


  // Software Guide : BeginLatex
  //
  // Having defined a pixel position with an index, it is then possible to
  // access the content of the pixel in the image. The \code{GetPixel()}
  // method allows us to get the value of the pixels.
  //
  // \index{itk::Image!GetPixel()}
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  ImageType::PixelType   pixelValue = image->GetPixel( pixelIndex );
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // The \code{SetPixel()} method allows us to set the value of the pixel.
  //
  // \index{itk::Image!SetPixel()}
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  image->SetPixel(   pixelIndex,   pixelValue+1  );
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // Please note that \code{GetPixel()} returns the pixel value using copy
  // and not reference semantics. Hence, the method cannot be used to
  // modify image data values.
  //
  // Remember that both \code{SetPixel()} and \code{GetPixel()} are inefficient
  // and should only be used for debugging or for supporting interactions like
  // querying pixel values by clicking with the mouse.
  //
  // Software Guide : EndLatex

  return EXIT_SUCCESS;
}