kCGImageSourceThumbnailMaxPixelSize
The maximum width and height of a thumbnail image, specified in pixels.
Declaration
let kCGImageSourceThumbnailMaxPixelSize: CFStringDiscussion
If this key is not specified, the width and height of a thumbnail is not limited and thumbnails may be as big as the image itself. If present, this key must be a CFNumber value. This key can be provided in the options dictionary that you pass to the function CGImageSourceCreateThumbnailAtIndex(_:_:_:).