article-programmaticalstyling4.swift

// Create an asset
let set = UIImageAsset()

// Define traits to be specific for the images
let darkTraits = UITraitCollection(traitsFrom: [UITraitCollection(userInterfaceStyle: .dark),
                                                UITraitCollection(displayScale: someDarkImage.scale)])
let lightTraits = UITraitCollection(traitsFrom: [UITraitCollection(userInterfaceStyle: .light),
                                                 UITraitCollection(displayScale: someLightImage.scale)])

// Register the images alongside the traits
set.register(someDarkImage, with: darkTraits)
set.register(someLightImage, with: lightTraits)

// Generated a combined image
let combinedImages = set.image(with: .current)