ios - CGAffineTransform 应用附加旋转

Question

从图库中选择视频后，我试图旋转它并将其保存在图库中。当我选择一个处于横向模式的视频时，我的旋转效果很好。但是，如果我选择一个处于纵向模式的视频，并尝试将其旋转到给定的角度。视频获得额外的旋转。

这是我的代码:

        let currentAsset = AVAsset( url: outputFileURL)
        let composition = AVMutableComposition.init()

        let videoComposition = AVMutableVideoComposition()
        videoComposition.frameDuration = CMTimeMake(1, 30)
        videoComposition.renderScale  = 1.0

        let compositionCommentaryTrack: AVMutableCompositionTrack? = composition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: kCMPersistentTrackID_Invalid)

        let compositionVideoTrack: AVMutableCompositionTrack? = composition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: kCMPersistentTrackID_Invalid)
        let videoDuration: CMTime = currentAsset.duration

        let clipVideoTrack:AVAssetTrack =  currentAsset.tracks(withMediaType: AVMediaType.video)[0]
        let audioTrack: AVAssetTrack = currentAsset.tracks(withMediaType: AVMediaType.audio)[0]

        try? compositionCommentaryTrack?.insertTimeRange(CMTimeRangeMake(kCMTimeZero, currentAsset.duration), of: audioTrack, at: kCMTimeZero)

        try? compositionVideoTrack?.insertTimeRange(CMTimeRangeMake(kCMTimeZero, currentAsset.duration ), of: clipVideoTrack, at: kCMTimeZero)
        var naturalSize = clipVideoTrack.naturalSize

        naturalSize = CGSize.init(width: naturalSize.width, height: naturalSize.height)
        videoComposition.renderSize = naturalSize
        let x = naturalSize.width
        let y = naturalSize.height

        let scale = CGFloat(1.0)
        let frontLayerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: compositionVideoTrack!)
        var rotationTransform = CGAffineTransform(translationX: x/2, y: y/2)
        rotationTransform = rotationTransform.rotated(by: angle)
        rotationTransform = rotationTransform.translatedBy(x: -x/2, y: -y/2)

        frontLayerInstruction.setTransform(rotationTransform, at: kCMTimeZero)

// saving video in gallery

        let MainInstruction = AVMutableVideoCompositionInstruction()
        MainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, composition.duration)
        MainInstruction.layerInstructions = [frontLayerInstruction]
        videoComposition.instructions = [MainInstruction]
        let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
        let videoPath = documentsPath+"/cropEditVideo.mov"

        let fileManager = FileManager.default

        if fileManager.fileExists(atPath: videoPath) {
            try! fileManager.removeItem(atPath: videoPath)
        }

        var exportSession = AVAssetExportSession.init(asset: composition, presetName: AVAssetExportPresetHighestQuality)
        exportSession?.outputFileType = AVFileType.mov
        exportSession?.videoComposition = videoComposition
        exportSession?.outputURL = URL.init(fileURLWithPath: videoPath)
        .
        .
        .
        .

我没有发布使用 AVAssetExportSession 保存视频的完整代码，因为我认为不需要它。

因此，如果我对视频应用 10 度旋转，它会以 280 度旋转保存。所以基本上是附加的，而且它只发生在肖像视频中。

任何帮助将不胜感激。

Answer 1

让我们考虑一下:

您有 2 个案例:

1. 您旋转横向视频，效果非常好；

2. 您旋转一个竖屏视频，效果非常好；

因此，问题不在于轮换；您尝试使用的肖像视频已经有了初始轮换!不用担心，这种情况经常发生并且通常是默认行为(我不确定为什么，我已经处理过很多次了)

一些例子:

AR Problem

AVAssetExportSession Problem

无需重写已经生成的代码；你的问题有解决方案here ，但是，如果您找不到答案，请在下方发表评论，我们可以解决!