UIImage+GIF.swift

extension Array where Element == UIImage {
    func gifData(frameDelay: TimeInterval = 0.2) -> Data? {
        let data = NSMutableData()
        guard let destination = CGImageDestinationCreateWithData(data, kUTTypeGIF, self.count, nil) else {
            return nil
        }
        
        let frameProperties: CFDictionary = [kCGImagePropertyGIFDictionary as String: [(kCGImagePropertyGIFDelayTime as String): frameDelay]] as CFDictionary
        let fileProperties: CFDictionary = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFLoopCount as String: 0]]  as CFDictionary
        CGImageDestinationSetProperties(destination, fileProperties)
        for image in self {
            if let cgImage = image.cgImage {
                CGImageDestinationAddImage(destination, cgImage, frameProperties)
            }
        }
        
        if !CGImageDestinationFinalize(destination) {
            return nil
        }
        
        return data as Data
    }
}