AdjacencyMatrixToEdgeTable

/* The output is:

10 20 30
40 50 60
70 80 90

+-----------------+------------------+
|                 | value            |
+-----------------+------------------+
| 2               | 30               |
| 1               | 20               |
| 0               | 10               |
| 2               | 60               |
| 1               | 50               |
| 0               | 40               |
| 2               | 90               |
| 1               | 80               |
| 0               | 70               |
+-----------------+------------------+

The first column is the column index of the item in the 'value' column.
The row index is given by the number of times we've previously seen the column
index. For some reason, zeros in the matrix are not reported in the table.

For example, the first row says that the value '30' is in column 2 of the matrix
(0-based indexing). Since we have not previously seen an item in column 2, it is
in row 0 of the matrix.

The fourth row says that the value '60' is also in column 2. We infer that '60'
is row 1 of the matrix because we have already seen one item (the '30') in
column 2.
*/

#include <vtkAdjacencyMatrixToEdgeTable.h>
#include <vtkArrayData.h>
#include <vtkArrayPrint.h>
#include <vtkDenseArray.h>
#include <vtkNew.h>
#include <vtkTable.h>

int main(int, char*[])
{
  vtkNew<vtkDenseArray<double>> array;

  array->Resize(3, 3);

  unsigned int counter{1};
  unsigned int scale{10};
  for (vtkIdType i = 0; i < array->GetExtents()[0].GetEnd(); i++)
  {
    for (vtkIdType j = 0; j < array->GetExtents()[1].GetEnd(); j++)
    {
      array->SetValue(i, j, counter * scale);
      counter++;
    }
  }

  vtkPrintMatrixFormat(std::cout, array.GetPointer());

  vtkNew<vtkArrayData> arrayData;
  arrayData->AddArray(array);

  vtkNew<vtkAdjacencyMatrixToEdgeTable> adjacencyMatrixToEdgeTable;
  adjacencyMatrixToEdgeTable->SetInputData(arrayData);
  adjacencyMatrixToEdgeTable->Update();

  adjacencyMatrixToEdgeTable->GetOutput()->Dump();

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(AdjacencyMatrixToEdgeTable)

find_package(VTK COMPONENTS 
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "AdjacencyMatrixToEdgeTable: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(AdjacencyMatrixToEdgeTable MACOSX_BUNDLE AdjacencyMatrixToEdgeTable.cxx )
  target_link_libraries(AdjacencyMatrixToEdgeTable PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS AdjacencyMatrixToEdgeTable
  MODULES ${VTK_LIBRARIES}
)

cd AdjacencyMatrixToEdgeTable/build

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./AdjacencyMatrixToEdgeTable