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# Description

Given a filename, render window and optionally a rgba value, take a screenshot of the render window and write it to a file. The extension of the filename determines what writer to use.

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## C++

### Declaration Section

    #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 <algorithm>
    #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);

    }

### Implementation Section

    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();
        }
        auto window_to_image_filter =
            vtkSmartPointer<vtkWindowToImageFilter>::New();
        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

### Usage

      WriteImage(f, renWin, false);