exportAnimatedGif.swift

import Cocoa

struct ImageConstants {
    static let gifDelayTime: NSNumber = 2
    static let gifLoopCount:NSNumber = 10
}

extension NSImage {
    
    //swift 2.0 translation/adaptation from https://gist.github.com/akisute/1141953
    //NSImage extension to export an array of NSImages to an animated gif at a given location
    func exportAnimatedGif(toFilePath filePath: NSURL, withImages images: [NSImage]) -> Bool {
        guard let fileDestination: CGImageDestination = CGImageDestinationCreateWithURL((filePath as CFURLRef), kUTTypeGIF, images.count, nil) else {
            return false
        }
        
        let frameProperties = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFDelayTime as String: ImageConstants.gifDelayTime]]
        let gifProperties = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFLoopCount as String: ImageConstants.gifLoopCount]]
        
        for (_, image) in images.enumerate() {
            let imageRef: CGImageRef =  NSImage.makeCGImage(image)
            CGImageDestinationAddImage(fileDestination, imageRef, (frameProperties as CFDictionaryRef))
        }
        
        CGImageDestinationSetProperties(fileDestination, (gifProperties as CFDictionaryRef))
        CGImageDestinationFinalize(fileDestination)
        return true
    }
    
    static func makeCGImage(image: NSImage)->CGImage {
        var imageRect:CGRect = CGRectMake(0, 0, image.size.width, image.size.height)
        return image.CGImageForProposedRect(&imageRect, context: nil, hints: nil)!
    }
}