in PhotoEditor/DetailPage.cpp [481:498]
void DetailPage::UpdateMainImageBrush()
{
MainImage().Source(m_imageSource);
MainImage().InvalidateArrange();
CreateEffectsGraph();
auto destinationBrush = m_compositor.CreateBackdropBrush();
auto graphicsEffectFactory = m_compositor.CreateEffectFactory(m_graphicsEffect, m_animatablePropertiesList);
m_combinedBrush = graphicsEffectFactory.CreateBrush();
m_combinedBrush.SetSourceParameter(L"Backdrop", destinationBrush);
auto effectSprite = m_compositor.CreateSpriteVisual();
effectSprite.Size(float2{ static_cast<float>(m_imageSource.PixelWidth()), static_cast<float>(m_imageSource.PixelHeight()) });
effectSprite.Brush(m_combinedBrush);
ElementCompositionPreview::SetElementChildVisual(MainImage(), effectSprite);
}