Example of vtkRenderWindow OffScreenRendering for Image export

exportScreenshot.cxx

// Enable OffScreen Rendering
renderWindow->OffScreenRenderingOn();

// Set renderWindow size
const int* windowSize = renderWindow->GetSize();
int W = windowSize[0];
int H = windowSize[1];
renderWindow->SetSize(d->exportWidthSpinBox->value(),d->exportHeightSpinBox->value());

// Get Image
vtkNew<vtkWindowToImageFilter> w2i;
w2i->SetInput(renderWindow);

// Create Writer
vtkNew<vtkPNGWriter> imageWriter;
imageWriter->SetInputConnection(w2i->GetOutputPort());
imageWriter->SetFileName("screenshot.png");

// Render
renderWindow->Render();

// Update filter
w2i->Modified();
w2i->Update();

// Write screenshot
imageWriter->Write();

// Reset renderwindow size
renderWindow->SetSize(W, H);

// Back to screen rendering
renderWindow->OffScreenRenderingOff();