14

我正在尝试从视频中获取缩略图并将其显示在我的表格视图中。这是我的代码：

- (UIImage *)imageFromVideoURL:(NSURL *)contentURL {
    AVAsset *asset = [AVAsset assetWithURL:contentURL];

    //  Get thumbnail at the very start of the video
    CMTime thumbnailTime = [asset duration];
    thumbnailTime.value = 25;

    //  Get image from the video at the given time
    AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset];

    CGImageRef imageRef = [imageGenerator copyCGImageAtTime:thumbnailTime actualTime:NULL error:NULL];
    UIImage *thumbnail = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);

    return thumbnail;
}

但图像总是返回黑色。怎么了？

4

8 回答 8

14

使用 Swift 5，作为 AVAsset 的扩展函数：

import AVKit

extension AVAsset {

    func generateThumbnail(completion: @escaping (UIImage?) -> Void) {
        DispatchQueue.global().async {
            let imageGenerator = AVAssetImageGenerator(asset: self)
            let time = CMTime(seconds: 0.0, preferredTimescale: 600)
            let times = [NSValue(time: time)]
            imageGenerator.generateCGImagesAsynchronously(forTimes: times, completionHandler: { _, image, _, _, _ in
                if let image = image {
                    completion(UIImage(cgImage: image))
                } else {
                    completion(nil)
                }
            })
        }
    }
}

用法：

            AVAsset(url: url).generateThumbnail { [weak self] (image) in
                DispatchQueue.main.async {
                    guard let image = image else { return }
                    self?.imageView.image = image
                }
            }
于 2019-04-05T08:16:07.370 回答
11

使用这个：Swift 3 -

func createThumbnailOfVideoFromFileURL(videoURL: String) -> UIImage? {
    let asset = AVAsset(url: URL(string: videoURL)!)
    let assetImgGenerate = AVAssetImageGenerator(asset: asset)
    assetImgGenerate.appliesPreferredTrackTransform = true
    let time = CMTimeMakeWithSeconds(Float64(1), 100)
    do {
        let img = try assetImgGenerate.copyCGImage(at: time, actualTime: nil)
        let thumbnail = UIImage(cgImage: img)
        return thumbnail
    } catch {
        return UIImage(named: "ico_placeholder")
    }
}

重要的提示 ：

您将需要在 if else 中使用它，因为它资源丰富。您必须将图像存储在数组或模型中，并检查是否在创建缩略图后引用缓存/数组，cellForRowAtIndexPath这样不会导致滚动延迟UITableView

于 2017-03-24T10:01:19.510 回答
4

只需使用此代码.. 传递您的视频 URL 并获取图像。

+(UIImage *)getPlaceholderImageFromVideo:(NSString *)videoURL {
    NSURL *url = [NSURL URLWithString:videoURL];
    AVAsset *asset = [AVAsset assetWithURL:url];
    AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
    CMTime time = [asset duration];
    time.value = 0;
    CGImageRef imageRef = [imageGenerator copyCGImageAtTime:time actualTime:NULL error:NULL];
    UIImage *thumbnail = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);
    return thumbnail;
}

希望，这就是你要找的。任何问题都可以回复我。:)

于 2017-07-18T10:47:50.850 回答
3 
//(Local URL)
NSURL *videoURL = [NSURL fileURLWithPath:filepath];// filepath is your video file path 



AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:videoURL options:nil];
AVAssetImageGenerator *generateImg = [[AVAssetImageGenerator alloc] initWithAsset:asset];
NSError *error = NULL;
CMTime time = CMTimeMake(1, 1);
CGImageRef refImg = [generateImg copyCGImageAtTime:time actualTime:NULL error:&error];
NSLog(@"error==%@, Refimage==%@", error, refImg);

UIImage *frameImage= [[UIImage alloc] initWithCGImage:refImg];
return frameImage;
于 2015-12-30T05:00:49.163 回答
2

请检查“从视频生成缩略图”的链接

https://littlebitesofcocoa.com/115-generating-thumbnails-from-videos

应用程序需要显示视频中内容的一个或多个缩略图（小型静止图像预览）是很常见的。但是，根据视频的来源，我们可能无法轻松访问它的预制缩略图。让我们看看如何使用 AVAssetImageGenerator 来抓取我们自己的。我们从视频的简单 NSURL 开始，它可以是本地的或远程的。我们将使用它创建一个 AVAsset，并将其创建到一个新的 AVAssetImageGenerator 对象。我们将配置生成器以应用首选变换，以便我们的缩略图处于正确的方向。

import AVFoundation

if let asset = AVAsset(URL: videoURL) {
   let durationSeconds = CMTimeGetSeconds(asset.duration)
   let generator = AVAssetImageGenerator(asset: asset)

   generator.appliesPreferredTrackTransform = true

   let time = CMTimeMakeWithSeconds(durationSeconds/3.0, 600)
   var thumbnailImage: CGImageRef 
   generator.generateCGImagesAsynchronouslyForTimes([NSValue(CMTime: time)]) { 
       (requestedTime: CMTime, thumbnail: CGImage?, actualTime: CMTime, result: AVAssetImageGeneratorResult, error: NSError?) in
      self.videoThumbnailImageView.image = UIImage(CGImage: thumbnail)
    }
}
于 2017-04-13T09:48:52.140 回答
1 
func getThumbnailFrom(path: URL) -> UIImage? {

        do {
            let asset = AVURLAsset(url: path , options: nil)
            let imgGenerator = AVAssetImageGenerator(asset: asset)
            imgGenerator.appliesPreferredTrackTransform = true
            let timestamp = asset.duration
            print("Timestemp:   \(timestamp)")
            let cgImage = try imgGenerator.copyCGImage(at: timestamp, actualTime: nil)
            let thumbnail = UIImage(cgImage: cgImage)
            return thumbnail
            } catch let error {
            print("*** Error generating thumbnail: \(error.localizedDescription)")
            return nil
          }
        }

本守则有效。

于 2019-06-17T06:57:52.423 回答
1

@Disha 答案的 Swift 4 代码：

let imageGenerator = AVAssetImageGenerator(asset: avAsset)
                let time = CMTime(seconds: seconds, preferredTimescale: 600)
                let times = [NSValue(time: time)]
                imageGenerator.generateCGImagesAsynchronously(forTimes: times, completionHandler: {
                    requestedTime, image, actualTime, result, error in
                    guard let cgImage = image else
                    {
                        print("No image!")
                        return
                    }
                    let uiImage = UIImage(cgImage: cgImage)
                    UIImageWriteToSavedPhotosAlbum(uiImage, nil, nil, nil);
                })
于 2019-01-22T20:07:00.887 回答
0

斯威夫特 5.2 版本：

您可以在此处找到我的原始帖子，我从rozochkin 的回答中获得灵感。

func getCurrentFrame() -> UIImage? {
    guard let player = self.player, let avPlayerAsset = player.currentItem?.asset else {return nil}
    let assetImageGenerator = AVAssetImageGenerator(asset: avPlayerAsset)
    assetImageGenerator.requestedTimeToleranceAfter = .zero
    assetImageGenerator.requestedTimeToleranceBefore = .zero
    assetImageGenerator.appliesPreferredTrackTransform = true
    let imageRef = try! assetImageGenerator.copyCGImage(at: player.currentTime(), actualTime: nil)
    let image = UIImage(cgImage: imageRef)
    return image
}

重要笔记：

requestedTimeToleranceAfter和requestedTimeToleranceBefore应设置为 .zero，因为根据源代码，“生成图像的实际时间 [...] 可能与请求的时间不同以提高效率”。

applyPreferredTrackTransform必须设置为TRUE（默认为 FALSE），否则你会得到一个糟糕的旋转帧。将此属性设置为 TRUE，您将获得您在播放器中真正看到的内容。

于 2020-05-11T17:41:02.463 回答