它确实起作用了。

func imageFromVideo(url: URL, at time: TimeInterval) -> UIImage? {
    let asset = AVURLAsset(url: url)

    let assetIG = AVAssetImageGenerator(asset: asset)
    assetIG.appliesPreferredTrackTransform = true
    assetIG.apertureMode = AVAssetImageGeneratorApertureModeEncodedPixels

    let cmTime = CMTime(seconds: time, preferredTimescale: 60)
    let thumbnailImageRef: CGImage
    do {
        thumbnailImageRef = try assetIG.copyCGImage(at: cmTime, actualTime: nil)
    } catch let error {
        print("Error: \(error)")
        return nil
    }

    return UIImage(cgImage: thumbnailImageRef)
}

但是请记住，这个函数是同步的，最好不要在主队列中调用它。
您可以执行以下任一操作：

DispatchQueue.global(qos: .background).async {
    let image = self.imageFromVideo(url: url, at: 0)

    DispatchQueue.main.async {
        self.imageView.image = image
    }
}

或者使用generateCGImagesAsynchronously代替copyCGImage。

以下是Dmitry解决方案的SWIFT 5替代方案，您不必担心自己处于哪个队列：

public func imageFromVideo(url: URL, at time: TimeInterval, completion: @escaping (UIImage?) -> Void) {
    DispatchQueue.global(qos: .background).async {
        let asset = AVURLAsset(url: url)

        let assetIG = AVAssetImageGenerator(asset: asset)
        assetIG.appliesPreferredTrackTransform = true
        assetIG.apertureMode = AVAssetImageGenerator.ApertureMode.encodedPixels

        let cmTime = CMTime(seconds: time, preferredTimescale: 60)
        let thumbnailImageRef: CGImage
        do {
            thumbnailImageRef = try assetIG.copyCGImage(at: cmTime, actualTime: nil)
        } catch let error {
            print("Error: \(error)")
            return completion(nil)
        }

        DispatchQueue.main.async {
            completion(UIImage(cgImage: thumbnailImageRef))
        }
    }
}

现在来使用它：

imageFromVideo(url: videoUrl, at: 0) { image in
   // Do something with the image here
}

你可以在iOS上轻松做到这一点。下面是一段代码片段，说明如何在Swift上做到这一点。

let url = Bundle.main.url(forResource: "video_name", withExtension: "mp4")
    let videoAsset = AVAsset(url: url!)
    
    let t1 = CMTime(value: 1, timescale: 1)
    let t2 = CMTime(value: 4, timescale: 1)
    let t3 = CMTime(value: 8, timescale: 1)
    let timesArray = [
        NSValue(time: t1),
        NSValue(time: t2),
        NSValue(time: t3)
    ]
    
    let generator = AVAssetImageGenerator(asset: videoAsset)
    generator.requestedTimeToleranceBefore = .zero
    generator.requestedTimeToleranceAfter = .zero
    
    generator.generateCGImagesAsynchronously(forTimes: timesArray ) { requestedTime, image, actualTime, result, error in
        
       let img = UIImage(cgImage: image!)
       
    }

您可以找到演示代码here和中等文章here。

下面是@Dmitry的async/await版本，可以帮助那些不喜欢完成处理程序的人

func imageFromVideo(url: URL, at time: TimeInterval) async throws -> UIImage {
        try await withCheckedThrowingContinuation({ continuation in
            DispatchQueue.global(qos: .background).async {
                let asset = AVURLAsset(url: url)
                
                let assetIG = AVAssetImageGenerator(asset: asset)
                assetIG.appliesPreferredTrackTransform = true
                assetIG.apertureMode = AVAssetImageGenerator.ApertureMode.encodedPixels
                
                let cmTime = CMTime(seconds: time, preferredTimescale: 60)
                let thumbnailImageRef: CGImage
                do {
                    thumbnailImageRef = try assetIG.copyCGImage(at: cmTime, actualTime: nil)
                } catch {
                    continuation.resume(throwing: error)
                    return
                }
                continuation.resume(returning: UIImage(cgImage: thumbnailImageRef))
            }
        })
    }

用法：

let vidUrl = <#your url#>
do {
    let firstFrame = try await imageFromVideo(url: vidUrl, at: 0)
    // do something with image
} catch {
    // handle error
}

如果你使用抛出函数，就像这样：

func someThrowingFunc() throws {
    let vidUrl = <#your url#>
    let firstFrame = try await imageFromVideo(url: vidUrl, at: 0)
    // do something with image
}