尝试使用 AVFoundation 为视频上的图像加水印

Question

我拍了一张png图像和一个视频进行水印，两者都是肖像。我已经在视频中为图像加水印。

加水印后，在横向模式下得到一个合并的视频，并在反时钟方向上翻转 90 度。我无法找出视频从纵向模式切换到横向模式的确切原因。当图像显示拉伸肖像时。请帮忙。提前谢谢。

使用以下代码：-

- (void)addWatermarkAtVideoFile:(NSURL *)videoURL image:(UIImage *)image withConvertedVideoUUID:(NSString *)convertedVideoUUID response:(void(^)(BOOL success, NSString *videoUUID, NSURL *videoPath))responseBlock {
    AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:videoURL options:nil];
    AVMutableComposition* mixComposition = [AVMutableComposition composition];

    AVAssetTrack *clipVideoTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    if(clipVideoTrack) {
        AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
        [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:clipVideoTrack atTime:kCMTimeZero error:nil];
        [compositionVideoTrack setPreferredTransform:[[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] preferredTransform]];
    }
    AVAssetTrack *clipAudioTrack = [[videoAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
    if(clipAudioTrack) {
        AVMutableCompositionTrack *compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
        [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset.duration) ofTrack:clipAudioTrack atTime:kCMTimeZero error:nil];
    }
    CGSize sizeOfVideo=[videoAsset naturalSize];
    //Image of watermark
    UIImage *myImage = image;
    CALayer *layerCa = [CALayer layer];
    layerCa.contents = (id)myImage.CGImage;
    layerCa.frame = CGRectMake(0, 0, sizeOfVideo.width, sizeOfVideo.height);
    layerCa.opacity = 1.0;
    CALayer *parentLayer=[CALayer layer];
    CALayer *videoLayer=[CALayer layer];
    parentLayer.frame=CGRectMake(0, 0, sizeOfVideo.width, sizeOfVideo.height);
    videoLayer.frame=CGRectMake(0, 0, sizeOfVideo.width, sizeOfVideo.height);
    [parentLayer addSublayer:videoLayer];
    [parentLayer addSublayer:layerCa];
    AVMutableVideoComposition *videoComposition=[AVMutableVideoComposition videoComposition] ;
    videoComposition.frameDuration=CMTimeMake(1, 30);
    videoComposition.renderSize=sizeOfVideo;
    videoComposition.animationTool=[AVVideoCompositionCoreAnimationTool videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:videoLayer inLayer:parentLayer];
    AVMutableVideoCompositionInstruction *instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    instruction.timeRange = CMTimeRangeMake(kCMTimeZero, [mixComposition duration]);
    AVAssetTrack *videoTrack = [[mixComposition tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];
    AVMutableVideoCompositionLayerInstruction* layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:videoTrack];
    instruction.layerInstructions = [NSArray arrayWithObject:layerInstruction];
    videoComposition.instructions = [NSArray arrayWithObject: instruction];
    //Creating temp path to save the converted video
    NSString* myDocumentPath = [self getDocumentDirectoryPathWithFileName:convertedVideoUUID];
    NSURL *outputFileURL = [[NSURL alloc] initFileURLWithPath:myDocumentPath];
    //Check if the file already exists then remove the previous file
    [self removeFileIfExistAtPAth:myDocumentPath];
    AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];
    exportSession.videoComposition=videoComposition;
    exportSession.outputURL = outputFileURL;
    exportSession.outputFileType = AVFileTypeQuickTimeMovie;
    [exportSession exportAsynchronouslyWithCompletionHandler:^{
        switch (exportSession.status)
        {
            case AVAssetExportSessionStatusCompleted:
                NSLog(@"Export OK");
                [self saveInPhotoAlbum:myDocumentPath];
                break;
            case AVAssetExportSessionStatusFailed:
                NSLog (@"AVAssetExportSessionStatusFailed: %@", exportSession.error);
                break;
            case AVAssetExportSessionStatusCancelled:
                NSLog(@"Export Cancelled");
                break;
        }
        BOOL statusSuccess = [exportSession status] == AVAssetExportSessionStatusCompleted;
        responseBlock(statusSuccess ? YES : NO, statusSuccess ? convertedVideoUUID : nil, statusSuccess ? outputFileURL : nil);
    }];
}

Answer 1

我认为这是 AVFoundation 的默认行为，它可能与水印功能无关。

您可以使用CGAffineTransform：

if(height > width) {
    CGAffineTransform rotationTransform = CGAffineTransformMakeRotation(M_PI_2);
    [layerInstruction setTransform:rotationTransform atTime:kCMTimeZero];
}

Answer 2

AVAsset的自然大小不考虑视频的最终旋转。
如果要正确放置游览水印，请考虑使用AVMutableVideoComposition的renderSize或应用一些转换。此代码段为您提供了资产的实际方向：

    func orientationForAsset(_ asset: AVAsset) -> (orientation: UIImageOrientation, isPortrait: Bool) {
        let videoTrack = asset.tracks(withMediaType: AVMediaTypeVideo).first!
        let transformMatrix = videoTrack.preferredTransform
        return orientationFromTransform(transformMatrix)
    }
    func orientationFromTransform(_ transform: CGAffineTransform) -> (orientation: UIImageOrientation, isPortrait: Bool) {
        var assetOrientation = UIImageOrientation.up
        var isPortrait = false
        if transform.a == 0 && transform.b == 1.0 && transform.c == -1.0 && transform.d == 0 {
            assetOrientation = .right
            isPortrait = true
        } else if transform.a == 0 && transform.b == -1.0 && transform.c == 1.0 && transform.d == 0 {
            assetOrientation = .left
            isPortrait = true
        } else if transform.a == 1.0 && transform.b == 0 && transform.c == 0 && transform.d == 1.0 {
            assetOrientation = .up
        } else if transform.a == -1.0 && transform.b == 0 && transform.c == 0 && transform.d == -1.0 {
            assetOrientation = .down
        }
        return (assetOrientation, isPortrait)
    }

有了这个，您可以考虑旋转获得实际尺寸。

func resolutionSizeForAsset(_ asset: AVAsset) -> CGSize? {
        guard let track = asset.tracks(withMediaType: AVMediaTypeVideo).first else { return nil }
        let size = track.naturalSize.applying(track.preferredTransform)
        return CGSize(width: fabs(size.width), height: fabs(size.height))
    }