in PhotoEditor/DetailPage.cpp [226:243]
void DetailPage::UpdateButtonImageBrush()
{
ButtonPreviewImage().Source(m_imageSource);
ButtonPreviewImage().InvalidateArrange();
CreateEffectsGraph();
auto destinationBrush = m_compositor.CreateBackdropBrush();
auto graphicsEffectFactory = m_compositor.CreateEffectFactory(m_graphicsEffect);
auto previewBrush = graphicsEffectFactory.CreateBrush();
previewBrush.SetSourceParameter(L"Backdrop", destinationBrush);
auto effectSprite = m_compositor.CreateSpriteVisual();
effectSprite.Size(float2{ 232, 64 });
effectSprite.Brush(previewBrush);
ElementCompositionPreview::SetElementChildVisual(ButtonPreviewImage(), effectSprite);
}