Method Initialize

Imaging/Core/vtkImagePointDataIterator.cxx:66–256

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void vtkImagePointDataIterator::Initialize(vtkImageData* image, const int extent[6],
  vtkImageStencilData* stencil, vtkAlgorithm* algorithm, int threadId)
{
  const int* dataExtent = image->GetExtent();
  if (extent == nullptr)
  {
    extent = dataExtent;
  }

  // Save the extent (will be adjusted if there is a stencil).
  bool emptyExtent = false;
  for (int i = 0; i < 6; i += 2)
  {
    this->Extent[i] = std::max(extent[i], dataExtent[i]);
    this->Extent[i + 1] = std::min(extent[i + 1], dataExtent[i + 1]);
    if (this->Extent[i] > this->Extent[i + 1])
    {
      emptyExtent = true;
    }
  }

  // Compute the increments for marching through the data.
  this->RowIncrement = dataExtent[1] - dataExtent[0] + 1;
  this->SliceIncrement = this->RowIncrement * (dataExtent[3] - dataExtent[2] + 1);

  int rowSpan, sliceSpan, volumeSpan;

  if (!emptyExtent)
  {
    // Compute the span of the image region to be covered.
    rowSpan = this->Extent[1] - this->Extent[0] + 1;
    sliceSpan = this->Extent[3] - this->Extent[2] + 1;
    volumeSpan = this->Extent[5] - this->Extent[4] + 1;
    this->Id = (this->Extent[0] - dataExtent[0]) +
      (this->Extent[2] - dataExtent[2]) * this->RowIncrement +
      (this->Extent[4] - dataExtent[4]) * this->SliceIncrement;

    // Compute the end increments (continuous increments).
    this->RowEndIncrement = this->RowIncrement - rowSpan;
    this->SliceEndIncrement =
      this->RowEndIncrement + this->SliceIncrement - this->RowIncrement * sliceSpan;
  }
  else
  {
    // Extent is empty, IsAtEnd() will immediately return "true"
    rowSpan = 0;
    sliceSpan = 0;
    volumeSpan = 0;
    this->Id = 0;
    this->RowEndIncrement = 0;
    this->SliceEndIncrement = 0;
    for (int i = 0; i < 6; i += 2)
    {
      this->Extent[i] = dataExtent[i];
      this->Extent[i + 1] = dataExtent[i] - 1;
    }
  }