# ImageWarp

VTKExamples/Cxx/Images/ImageWarp

### Description

Combining the imaging and visualization pipelines to deform an image in the z-direction. The vtkMergeFilter is used to combine the warped surface with the original color data.

Info

See Figure 10-17 in Chapter 10 the VTK Textbook.

Other Languages

See (Python)

### Code

ImageWarp.cxx

    /*
     * This example shows how to combine data from both the imaging
     *  and graphics pipelines. The vtkMergeData filter is used to
     *  merge the data from each together.
    */
    #include <vtkActor.h>
    #include <vtkBMPReader.h>
    #include <vtkCamera.h>
    #include <vtkDataSetMapper.h>
    #include <vtkImageDataGeometryFilter.h>
    #include <vtkImageLuminance.h>
    #include <vtkMergeFilter.h>
    #include <vtkNamedColors.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>
    #include <vtkSmartPointer.h>
    #include <vtkWarpScalar.h>

    #include <array>
    #include <iomanip>
    #include <iostream>
    #include <string>

    int main(int argc, char* argv[])
    {

      if (argc < 2)
      {
        std::cout << "Usage: " << argv[0] << " fileName" << std::endl;
        std::cout << "where: fileName is the masonry.bmp file." << std::endl;
        return EXIT_FAILURE;
      }

      std::string fileName = argv[1];

      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      // Set the background color.
      std::array<unsigned char , 4> bkg{{60, 93, 144, 255}};
        colors->SetColor("BkgColor", bkg.data());

      // Read in an image and compute a luminance value-> The image is extracted
      // as a set of polygons (vtkImageDataGeometryFilter). We then will
      // warp the plane using the scalar (luminance) values.
      //
      vtkSmartPointer<vtkBMPReader> reader = vtkSmartPointer<vtkBMPReader>::New();
      reader->SetFileName(fileName.c_str());
      // Convert the image to a grey scale.
      vtkSmartPointer<vtkImageLuminance> luminance =
        vtkSmartPointer<vtkImageLuminance>::New();
      luminance->SetInputConnection(reader->GetOutputPort());
      // Pass the data to the pipeline as polygons.
      vtkSmartPointer<vtkImageDataGeometryFilter> geometry =
        vtkSmartPointer<vtkImageDataGeometryFilter>::New();
      geometry->SetInputConnection(luminance->GetOutputPort());
      // Warp the data in a direction perpendicular to the image plane.
      vtkSmartPointer<vtkWarpScalar> warp = vtkSmartPointer<vtkWarpScalar>::New();
      warp->SetInputConnection(geometry->GetOutputPort());
      warp->SetScaleFactor(-0.1);

      // Use vtkMergeFilter to combine the original image with the warped geometry.
      vtkSmartPointer<vtkMergeFilter> merge =
        vtkSmartPointer<vtkMergeFilter>::New();
      merge->SetGeometryConnection(warp->GetOutputPort());
      merge->SetScalarsConnection(reader->GetOutputPort());
      vtkSmartPointer<vtkDataSetMapper> mapper =
        vtkSmartPointer<vtkDataSetMapper>::New();
      mapper->SetInputConnection(merge->GetOutputPort());
      mapper->SetScalarRange(0, 255);
      vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
      actor->SetMapper(mapper);

      // Create the rendering window, renderer, and interactive renderer.
      //
      vtkSmartPointer<vtkRenderer> ren = vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renWin =
        vtkSmartPointer<vtkRenderWindow>::New();
      renWin->AddRenderer(ren);

      vtkSmartPointer<vtkRenderWindowInteractor> iren =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      iren->SetRenderWindow(renWin);

      // Add the actors to the renderer, set the background and size.
      ren->AddActor(actor);
      ren->ResetCamera();
      ren->SetBackground(colors->GetColor3d("BkgColor").GetData());
      // ren->GetActiveCamera()->Azimuth(20);
      // ren->GetActiveCamera()->Elevation(30);
      // ren->ResetCameraClippingRange();
      // ren->GetActiveCamera()->Zoom(1.3);
      ren->GetActiveCamera()->SetPosition(-100, -130, 325);
      ren->GetActiveCamera()->SetFocalPoint(105, 114, -29);
      ren->GetActiveCamera()->SetViewUp(0.51, 0.54, 0.67);
      ren->ResetCameraClippingRange();

      renWin->SetSize(512, 512);

      // Render the image.
      renWin->Render();
      iren->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ImageWarp)

    find_package(VTK COMPONENTS
      vtkCommonColor
      vtkCommonCore
      vtkFiltersCore
      vtkFiltersGeneral
      vtkFiltersGeometry
      vtkIOImage
      vtkImagingColor
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ImageWarp: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(ImageWarp MACOSX_BUNDLE ImageWarp.cxx )
      target_link_libraries(ImageWarp PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ImageWarp MACOSX_BUNDLE ImageWarp.cxx )
      target_link_libraries(ImageWarp PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ImageWarp
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ImageWarp

Click here to download ImageWarp and its CMakeLists.txt file. Once the tarball ImageWarp.tar has been downloaded and extracted,

    cd ImageWarp/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

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

Build the project:

    make

and run it:

    ./ImageWarp

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.