Skip to content

ImageWriter

vtk-examples/Cxx/IO/ImageWriter


Description

A generic function WriteImage() is provided that selects what image writer to use based on the file extenstion and then writes the render window to the file. The following formats are supported: BMP, JPEG, PNM, PNG, PostScript, TIFF.

If no file extension is specified, PNG is assumed.

The function WriteImage() is also available in the Snippets.

Other languages

See (Python)

Question

If you have a question about this example, please use the VTK Discourse Forum

Code

ImageWriter.cxx

#include <vtkActor.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSmartPointer.h>
#include <vtkSphereSource.h>

#include <vtkBMPWriter.h>
#include <vtkImageWriter.h>
#include <vtkJPEGWriter.h>
#include <vtkPNGWriter.h>
#include <vtkPNMWriter.h>
#include <vtkPostScriptWriter.h>
#include <vtkTIFFWriter.h>
#include <vtkWindowToImageFilter.h>

#include <array>
#include <locale>
#include <string>

namespace {

/**
 *  Write the render window view to an image file.
 *
 *  Image types supported are:
 *    BMP, JPEG, PNM, PNG, PostScript, TIFF.
 *  The default parameters are used for all writers, change as needed.
 *
 *  @param fileName The file name, if no extension then PNG is assumed.
 *  @param renWin The render window.
 *  @param rgba Used to set the buffer type.
 *
 */
void WriteImage(std::string const& fileName, vtkRenderWindow* renWin,
                bool rgba = true);
} // namespace

int main(int, char*[])
{

  vtkNew<vtkNamedColors> colors;

  // Set the background color.
  std::array<unsigned char, 4> bkg{{26, 51, 102, 255}};
  colors->SetColor("BkgColor", bkg.data());

  // Create the rendering window, renderer, and interactive renderer.
  vtkNew<vtkRenderer> ren;
  vtkNew<vtkRenderWindow> renWin;
  renWin->AddRenderer(ren);
  vtkNew<vtkRenderWindowInteractor> iren;
  iren->SetRenderWindow(renWin);

  // Create the source.
  vtkNew<vtkSphereSource> source;
  source->SetCenter(0, 0, 0);
  source->SetRadius(5.0);

  // mapper
  vtkNew<vtkPolyDataMapper> mapper;
  mapper->SetInputConnection(source->GetOutputPort());

  // actor
  vtkNew<vtkActor> actor;
  actor->SetMapper(mapper);

  // color the actor
  actor->GetProperty()->SetColor(colors->GetColor3d("Yellow").GetData());

  // assign actor to the renderer
  ren->AddActor(actor);
  ren->SetBackground(colors->GetColor3d("BkgColor").GetData());

  renWin->SetWindowName("ImageWriter");
  renWin->Render();

  std::vector<std::string> ext = {{""},      {".png"}, {".jpg"}, {".ps"},
                                  {".tiff"}, {".bmp"}, {".pnm"}};
  std::vector<std::string> filenames;
  std::transform(ext.begin(), ext.end(), std::back_inserter(filenames),
                 [](const std::string& e) { return "ImageWriter" + e; });
  filenames[0] = filenames[0] + '1';
  for (auto f : filenames)
  {
    WriteImage(f, renWin, false);
  }

  iren->Initialize();
  iren->Start();

  return EXIT_SUCCESS;
}

namespace {

void WriteImage(std::string const& fileName, vtkRenderWindow* renWin, bool rgba)
{
  if (!fileName.empty())
  {
    std::string fn = fileName;
    std::string ext;
    auto found = fn.find_last_of(".");
    if (found == std::string::npos)
    {
      ext = ".png";
      fn += ext;
    }
    else
    {
      ext = fileName.substr(found, fileName.size());
    }
    std::locale loc;
    std::transform(ext.begin(), ext.end(), ext.begin(),
                   [=](char const& c) { return std::tolower(c, loc); });
    auto writer = vtkSmartPointer<vtkImageWriter>::New();
    if (ext == ".bmp")
    {
      writer = vtkSmartPointer<vtkBMPWriter>::New();
    }
    else if (ext == ".jpg")
    {
      writer = vtkSmartPointer<vtkJPEGWriter>::New();
    }
    else if (ext == ".pnm")
    {
      writer = vtkSmartPointer<vtkPNMWriter>::New();
    }
    else if (ext == ".ps")
    {
      if (rgba)
      {
        rgba = false;
      }
      writer = vtkSmartPointer<vtkPostScriptWriter>::New();
    }
    else if (ext == ".tiff")
    {
      writer = vtkSmartPointer<vtkTIFFWriter>::New();
    }
    else
    {
      writer = vtkSmartPointer<vtkPNGWriter>::New();
    }
    vtkNew<vtkWindowToImageFilter> window_to_image_filter;
    window_to_image_filter->SetInput(renWin);
    window_to_image_filter->SetScale(1); // image quality
    if (rgba)
    {
      window_to_image_filter->SetInputBufferTypeToRGBA();
    }
    else
    {
      window_to_image_filter->SetInputBufferTypeToRGB();
    }
    // Read from the front buffer.
    window_to_image_filter->ReadFrontBufferOff();
    window_to_image_filter->Update();

    writer->SetFileName(fn.c_str());
    writer->SetInputConnection(window_to_image_filter->GetOutputPort());
    writer->Write();
  }
  else
  {
    std::cerr << "No filename provided." << std::endl;
  }

  return;
}

} // namespace

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ImageWriter)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  FiltersSources
  IOImage
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ImageWriter: 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(ImageWriter MACOSX_BUNDLE ImageWriter.cxx )
  target_link_libraries(ImageWriter PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS ImageWriter
  MODULES ${VTK_LIBRARIES}
)

Download and Build ImageWriter

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

cd ImageWriter/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:

./ImageWriter

WINDOWS USERS

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