CGRectAspectScale.swift

extension CGRect {
  func scaled(toFillSize targetSize: CGSize) -> CGRect {
    var scaledRect = self
    switch (size.aspect, targetSize.aspect) {
    case (.portrait, .portrait), (.portrait, .square):
      scaledRect.size.height = width / targetSize.aspectRatio
      scaledRect.size.width = width
      if scaledRect.height > height {
        scaledRect.size = size
      }
      scaledRect.origin.y -= (scaledRect.height - height) / 2.0
    case (.portrait, .landscape), (.square, .landscape):
      scaledRect.size.height = width / targetSize.aspectRatio
      scaledRect.size.width = width
      if scaledRect.height > height {
        scaledRect.size = size
      }
      scaledRect.origin.y -= (scaledRect.height - height) / 2.0
    case (.landscape, .portrait), (.square, .portrait):
      scaledRect.size.height = height
      scaledRect.size.width = height * targetSize.aspectRatio
      if scaledRect.width > width {
        scaledRect.size = size
      }
      scaledRect.origin.x -= (scaledRect.width - width) / 2.0
    case (.landscape, .landscape), (.landscape, .square):
      scaledRect.size.height = height
      scaledRect.size.width = height * targetSize.aspectRatio
      if scaledRect.size.width > width {
        scaledRect.size = size
      }
      scaledRect.origin.x -= (scaledRect.width - width) / 2.0
    case (.square, .square):
      return self
    }
    return scaledRect.integral
  }
}