Function vtkImageReaderUpdate2

IO/Image/vtkImageReader.cxx:187–346

// templated to handle different data types.
template <class IT, class OT>
void vtkImageReaderUpdate2(vtkImageReader* self, vtkImageData* data, IT* inPtr, OT* outPtr)
{
  vtkIdType inIncr[3], outIncr[3];
  OT *outPtr0, *outPtr1, *outPtr2;
  long streamSkip0, streamSkip1;
  unsigned long streamRead;
  int idx0, idx1, idx2, pixelRead;
  int inExtent[6];
  int dataExtent[6];
  int comp, pixelSkip;
  long filePos, correction = 0;
  unsigned long count = 0;
  vtkTypeUInt64 DataMask;
  unsigned long target;

  // Get the requested extents.
  data->GetExtent(inExtent);

  // Convert them into to the extent needed from the file.
  self->ComputeInverseTransformedExtent(inExtent, dataExtent);

  // get and transform the increments
  data->GetIncrements(inIncr);
  self->ComputeInverseTransformedIncrements(inIncr, outIncr);

  DataMask = self->GetDataMask();

  // compute outPtr2
  outPtr2 = outPtr;
  if (outIncr[0] < 0)
  {
    outPtr2 = outPtr2 - outIncr[0] * (dataExtent[1] - dataExtent[0]);
  }
  if (outIncr[1] < 0)
  {
    outPtr2 = outPtr2 - outIncr[1] * (dataExtent[3] - dataExtent[2]);
  }
  if (outIncr[2] < 0)
  {
    outPtr2 = outPtr2 - outIncr[2] * (dataExtent[5] - dataExtent[4]);
  }

  // length of a row, num pixels read at a time
  pixelRead = dataExtent[1] - dataExtent[0] + 1;
  streamRead = static_cast<unsigned long>(pixelRead * self->GetDataIncrements()[0]);
  streamSkip0 = (long)(self->GetDataIncrements()[1] - streamRead);
  streamSkip1 = (long)(self->GetDataIncrements()[2] -
    (dataExtent[3] - dataExtent[2] + 1) * self->GetDataIncrements()[1]);
  pixelSkip = data->GetNumberOfScalarComponents();

  // read from the bottom up
  if (!self->GetFileLowerLeft())
  {
    streamSkip0 = (long)(-static_cast<long>(streamRead) - self->GetDataIncrements()[1]);
    streamSkip1 = (long)(self->GetDataIncrements()[2] +
      (dataExtent[3] - dataExtent[2] + 1) * self->GetDataIncrements()[1]);
  }