Function ComputeGlobalOrigin

Filters/Parallel/vtkAlignImageDataSetFilter.cxx:38–83

}

bool ComputeGlobalOrigin(vtkVector3d& origin, const std::vector<vtkImageData*>& images,
  vtkMultiProcessController* controller, const int minimumExtent[3])
{
  // First, confirm that spacing is compatible. All images must have the same
  // spacing otherwise we cannot pick a valid global origin/extent.
  vtkVector3d spacing =
    images.empty() ? vtkVector3d(0.0) : vtkVector3d(images.front()->GetSpacing());
  for (auto* image : images)
  {
    if (image->GetNumberOfPoints() > 0)
    {
      const vtkVector3d imgSpacing(image->GetSpacing());
      if (spacing != imgSpacing)
      {
        spacing = vtkVector3d(VTK_DOUBLE_MAX);
      }
    }
  }

  vtkVector3d globalSpacing = AllGather(spacing, controller);
  if (!IsSpacingValid(globalSpacing))
  {
    vtkLogF(ERROR, "Cannot determine acceptable global spacing.");
    return false;
  }

  // Compute global bounds to determine the global image origin.
  vtkBoundingBox bbox;
  for (auto* image : images)
  {
    bbox.AddBounds(image->GetBounds());
  }

  vtkBoundingBox globalBounds;
  controller->AllReduce(bbox, globalBounds);
  globalBounds.GetMinPoint(origin.GetData());

  // globalOrigin is based on the extent set at (0, 0, 0) right now. we need to adjust
  // globalOrigin based on minimumExtent though.
  for (int cc = 0; cc < 3; ++cc)
  {
    origin[cc] -= minimumExtent[cc] * spacing[cc];
  }

  return true;
}

}