Method ComputeStartOffset

IO/Image/vtkImageReader.cxx:151–181

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//------------------------------------------------------------------------------
vtkTypeInt64 vtkImageReader::ComputeStartOffset(int dataExtent[6], int idx)
{
  vtkTypeInt64 startOffset;

  // convert data extent into constants that can be used to seek.
  startOffset =
    static_cast<std::streamoff>(dataExtent[0] - this->DataExtent[0]) * this->DataIncrements[0];

  if (this->FileLowerLeft)
  {
    startOffset +=
      static_cast<std::streamoff>(dataExtent[2] - this->DataExtent[2]) * this->DataIncrements[1];
  }
  else
  {
    startOffset +=
      static_cast<std::streamoff>(this->DataExtent[3] - this->DataExtent[2] - dataExtent[2]) *
      this->DataIncrements[1];
  }

  // handle three and four dimensional files
  if (this->GetFileDimensionality() >= 3)
  {
    startOffset +=
      static_cast<std::streamoff>(dataExtent[4] - this->DataExtent[4]) * this->DataIncrements[2];
  }

  startOffset += this->GetHeaderSize(idx);

  return startOffset;
}

//------------------------------------------------------------------------------
// This function reads in one data of data.