video-to-gif-asset-reader.swift

let startTime = CFAbsoluteTimeGetCurrent()

let totalFrames = 882

// `url` is a locally saved MP4
let asset = AVURLAsset(url: url)
let reader = try! AVAssetReader(asset: asset)
let videoTrack = asset.tracks(withMediaType: .video).first!

let outputSettings: [String: Any] = [
    kCVPixelBufferPixelFormatTypeKey as String: kCVPixelFormatType_32ARGB
]

let readerOutput = AVAssetReaderTrackOutput(track: videoTrack, outputSettings: outputSettings)

reader.add(readerOutput)
reader.startReading()

var sample: CMSampleBuffer? = readerOutput.copyNextSampleBuffer()
let context = CIContext(options: nil)

let delayBetweenFrames: CGFloat = 0.03030303

let fileProperties: [String: Any] = [
    kCGImagePropertyGIFDictionary as String: [
        kCGImagePropertyGIFLoopCount as String: 0
    ]
]

let frameProperties: [String: Any] = [
    kCGImagePropertyGIFDictionary as String: [
        kCGImagePropertyGIFDelayTime: delayBetweenFrames
    ]
]

let resultingFilename = String(format: "%@_%@", ProcessInfo.processInfo.globallyUniqueString, "html5gif.gif")
let resultingFileURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(resultingFilename)
let destination = CGImageDestinationCreateWithURL(resultingFileURL as CFURL, kUTTypeGIF, totalFrames, nil)!
CGImageDestinationSetProperties(destination, fileProperties as CFDictionary)

let operationQueue = OperationQueue()
operationQueue.maxConcurrentOperationCount = 1

while (sample != nil) {
    if let newSample = sample {
        let pixelBuffer = CMSampleBufferGetImageBuffer(newSample)!
        let ciImage = CIImage(cvImageBuffer: pixelBuffer).transformed(by: CGAffineTransform(scaleX: 0.6, y: 0.6))
        let cgImage = context.createCGImage(ciImage, from: ciImage.extent)!
        
        operationQueue.addOperation {
            CGImageDestinationAddImage(destination, cgImage, frameProperties as CFDictionary)
        }
    }
    
    sample = readerOutput.copyNextSampleBuffer()
}

operationQueue.waitUntilAllOperationsAreFinished()

let result = CGImageDestinationFinalize(destination)

print("Did it succeed?", result)

PHPhotoLibrary.shared().performChanges({
    PHAssetCreationRequest.creationRequestForAssetFromImage(atFileURL: resultingFileURL)
}) { (saved, err) in
    print("Saved?", saved)
}