SwiftImage （旧 EasyImagy ）では Image に withUnsafeMutableBufferPointer とか付けてるよ。生でピクセル配列を扱いたいときとか用に。 https://github.com/koher/swift-image/blob/dev-0.7.0/Sources/EasyImagy/Image.swift#L58-L60

SwiftImage: A Swift library for image processing with Swifty APIs - koher/swift-image