video-to-gif.swift

import UIKit
import AVFoundation
import Photos
import MobileCoreServices

class ViewController: UIViewController {
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
    
        startVideoToGIFProcess()
    }
    
    func startVideoToGIFProcess() {
        // Download the video and write it to temp storage
        print("Downloading video…")
        let data = try! Data(contentsOf: URL(string: "https://i.imgur.com/dXxP7a9.mp4")!)
        let fileName = String(format: "%@_%@", ProcessInfo.processInfo.globallyUniqueString, "html5gif.mp4")
        let fileURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(fileName)
        try! data.write(to: fileURL, options: [.atomic])
        
        createGIF(fromVideoAtURL: fileURL)
    }
    
    func createGIF(fromVideoAtURL url: URL) {
        print("Downloaded!")
        
        let frameRate: Int = 20
        let duration: TimeInterval = 9.68
        let totalFrames = Int(duration * TimeInterval(frameRate))
        let delayBetweenFrames: TimeInterval = 1.0 / TimeInterval(frameRate)
        
        var timeValues: [NSValue] = []
        
        for frameNumber in 0 ..< totalFrames {
            let seconds = TimeInterval(delayBetweenFrames) * TimeInterval(frameNumber)
            let time = CMTime(seconds: seconds, preferredTimescale: Int32(NSEC_PER_SEC))
            timeValues.append(NSValue(time: time))
        }
        
        let asset = AVURLAsset(url: url)
        let generator = AVAssetImageGenerator(asset: asset)
        generator.requestedTimeToleranceBefore = CMTime(seconds: 0.05, preferredTimescale: 600)
        generator.requestedTimeToleranceAfter = CMTime(seconds: 0.05, preferredTimescale: 600)
        
        let sizeModifier: CGFloat = 0.1
        generator.maximumSize = CGSize(width: 450.0 * sizeModifier, height: 563.0 * sizeModifier)
        
        // Set up resulting image
        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)
        
        print("Converting to GIF…")
        var framesProcessed = 0
        let startTime = CFAbsoluteTimeGetCurrent()
        
        generator.generateCGImagesAsynchronously(forTimes: timeValues) { (requestedTime, resultingImage, actualTime, result, error) in
            guard let resultingImage = resultingImage else { return }
            
            framesProcessed += 1
            
            CGImageDestinationAddImage(destination, resultingImage, frameProperties as CFDictionary)
            
            if framesProcessed == totalFrames {
                let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
                print("Done converting to GIF! Frames processed: \(framesProcessed) • Total time: \(timeElapsed) s.")
                
                // Save to Photos just to check…
                let result = CGImageDestinationFinalize(destination)
                print("Did it succeed?", result)
                
                if result {
                    print("Saving to Photos…")

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

ffmpeg version using mobile ffmpeg with the mobile-ffmpeg-min specification:

do {
    let data = try Data(contentsOf: URL(string: "https://i.imgur.com/dXxP7a9.mp4")!)

    let fileName = String(format: "%@_%@", ProcessInfo.processInfo.globallyUniqueString, "html5gif.mp4")
    let fileURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(fileName)

    try data.write(to: fileURL, options: [.atomic])

    print("Downloaded, starting GIF conversion…")

    let outfileName = String(format: "%@_%@", ProcessInfo.processInfo.globallyUniqueString, "outfile.gif")
    let outfileURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(outfileName)

    let startTime = CFAbsoluteTimeGetCurrent()

    let _ = MobileFFmpeg.execute("-i \(fileURL.path) -vf fps=20,scale=450:-1 \(outfileURL.path)")

    let timeElapsed = CFAbsoluteTimeGetCurrent() - startTime
    print("Time elapsed: \(timeElapsed) s.")

    PHPhotoLibrary.shared().performChanges({
        PHAssetCreationRequest.creationRequestForAssetFromImage(atFileURL: outfileURL)
    }) { (saved, err) in
        print("Saved?", saved)
    }
} catch {
    print("Error was:", error)
}

About 10x faster on devices like iPhone 6s. 😃The size of ffmpeg means my app size would increase by about 30% for a single feature. 😭

Exporting this MP4 to GIF on an iPhone 6s takes 29 seconds with the AVFoundation solution and a little under 3 seconds with ffmpeg. Resulting GIF looks very similar in terms of quality (which is to say pretty good for a GIF).

ffmpeg GIF: https://christianselig.com/ffmpeg.gif
AVFoundation GIF: https://christianselig.com/avasset.gif

Hey @christianselig thanks so much for releasing this code! What's the license for the code?

@bl791 Oo, fair question! Let's go with MIT! Also for what it's worth I have a vague memory of getting the "native" version to a speed that matched ffmpeg-mobile. I don't totally remember what I did, but I don't think it was anything too intense, I think I was just getting the iOS native version to do more and had some unnecessary parts, so I don't think you need ffmpeg-mobile by any means (I definitely did not end up shipping it in my app purely because of the size of the library)

Nice, thank you so much!

Sorry, one more question - will this work for very large GIFs (ie over a minute)?

@bl791 I looked in Apollo and I have this code, so I'm going to guess right around a minute should be the maximum otherwise iOS will probably run out of memory due to GIFs being a very inefficient video storage format:

/// If the video is any longer than this, do not offer to save it as a GIF
static var upperLimitDurationThresholdForGIF: TimeInterval = 65.0

Thanks!