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无法使用swift中的缓存生成视频缩略图

nscache avfoundation swift3 swift ios

Marian Petrisor · 技术社区 · 7 年前

一直在努力工作。我正在生成视频缩略图,但它在集合视图中的加载量非常大。我想缓存它们,但找不到解决方案。

这是我使用的代码:

func previewImageFromVideo(url:NSURL) -> UIImage? {


    let asset = AVAsset(url: url as URL)
    let imageGenerator = AVAssetImageGenerator(asset:asset)
    imageGenerator.appliesPreferredTrackTransform = true
    imageGenerator.maximumSize = CGSize(width: 250, height: 120)

    var time = asset.duration
    time.value = min(time.value,2)

    do {
        let imageRef = try imageGenerator.copyCGImage(at: time, actualTime: nil)
        return UIImage(cgImage: imageRef)
    } catch {
        return nil
    }
}

我把它们做得很小,但每次都要连接到服务器。请帮忙。

2 回复 | 直到 7 年前

par 7 年前

URLCache

func previewImageFromVideo(url: NSURL) -> UIImage? {
    let url = url as URL
    let request = URLRequest(url: url)
    let cache = URLCache.shared

    if
        let cachedResponse = cache.cachedResponse(for: request),
        let image = UIImage(data: cachedResponse.data)
    {
        return image
    }

    let asset = AVAsset(url: url)
    let imageGenerator = AVAssetImageGenerator(asset: asset)
    imageGenerator.appliesPreferredTrackTransform = true
    imageGenerator.maximumSize = CGSize(width: 250, height: 120)

    var time = asset.duration
    time.value = min(time.value, 2)

    var image: UIImage?

    do {
        let cgImage = try imageGenerator.copyCGImage(at: time, actualTime: nil)
        image = UIImage(cgImage: cgImage)
    } catch { }

    if
        let image = image,
        let data = UIImagePNGRepresentation(image),
        let response = HTTPURLResponse(url: url, statusCode: 200, httpVersion: nil, headerFields: nil)
    {
        let cachedResponse = CachedURLResponse(response: response, data: data)

        cache.storeCachedResponse(cachedResponse, for: request)
    }

    return image
}

Yassine En 7 年前

 let videoURL = URL(fileURLWithPath: self.videoPath)
 let thumbnailImage = videoURL.createVideoThumbnail()

let imageCache = NSCache<AnyObject, AnyObject>()

extension URL {

   func createVideoThumbnail() -> UIImage? {

    if let imageFromCache = imageCache.object(forKey: self as AnyObject) as? UIImage {
        return imageFromCache
    }

    let asset = AVAsset(url: self)
    let imageGenerator = AVAssetImageGenerator(asset: asset)
    imageGenerator.appliesPreferredTrackTransform = true
    imageGenerator.maximumSize = CGSize(width: 250, height: 120)

    var time = asset.duration
    time.value = min(time.value, 2)

    do {
        let cgImage = try imageGenerator.copyCGImage(at: time, actualTime: nil)
        let image = UIImage(cgImage: cgImage)
        imageCache.setObject(image as AnyObject, forKey: self as AnyObject)
        return image
    } catch let err {
        print(err)
     }
    return UIImage()
}