一直在努力让它发挥作用。我正在生成视频缩略图,但它在集合视图中加载非常重。我想缓存它们,但找不到解决方案。
这是我正在使用的代码:
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,但每次仍然连接到服务器。请帮忙。
您可以使用URLCache https://developer.apple.com/documentation/foundation/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
}
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