Swift 中的视频合并方向

Question

我正在使用 ray wenderlich 中的视频合并教程。我总是旋转 90 度 video.When 我添加了一些我的视频看不到的不同咖啡因旋转代码。你能告诉我包含 CGAffineTransformMakeRotation 的代码吗？

我的代码如下

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)
}


func videoCompositionInstructionForTrack(track: AVCompositionTrack, asset: AVAsset) -> AVMutableVideoCompositionLayerInstruction {
    // 1
    let instruction = AVMutableVideoCompositionLayerInstruction(assetTrack: track)
    // 2
    let assetTrack = asset.tracksWithMediaType(AVMediaTypeVideo)[0] as! AVAssetTrack

    // 3
    var transform = assetTrack.preferredTransform
    let assetInfo = orientationFromTransform(transform)
    var scaleToFitRatio = UIScreen.mainScreen().bounds.width / assetTrack.naturalSize.width

    if assetInfo.isPortrait {
        // 4
        print("ppppp")
        scaleToFitRatio = UIScreen.mainScreen().bounds.width / assetTrack.naturalSize.height
        let scaleFactor = CGAffineTransformMakeScale(scaleToFitRatio, scaleToFitRatio)

        //instruction.setTransform(t2, atTime: kCMTimeZero)


        instruction.setTransform(CGAffineTransformConcat(assetTrack.preferredTransform, scaleFactor),
            atTime: kCMTimeZero)




    } else {
        // 5
        let scaleFactor = CGAffineTransformMakeScale(scaleToFitRatio, scaleToFitRatio)
        var concat = CGAffineTransformConcat(CGAffineTransformConcat(assetTrack.preferredTransform, scaleFactor), CGAffineTransformMakeTranslation(0, UIScreen.mainScreen().bounds.width / 2))
        if assetInfo.orientation == .Down {
            print("down")
            let fixUpsideDown = CGAffineTransformMakeRotation(CGFloat(M_PI))
            let windowBounds = UIScreen.mainScreen().bounds
            let yFix = assetTrack.naturalSize.height + windowBounds.height
            let centerFix = CGAffineTransformMakeTranslation(assetTrack.naturalSize.width, yFix)
            concat = CGAffineTransformConcat(CGAffineTransformConcat(fixUpsideDown, centerFix), scaleFactor)
        }
        instruction.setTransform(concat, atTime: kCMTimeZero)
    }

    return instruction
}

Answer 1

CGAffineTransformRotate 围绕一个点运行。

当您旋转视频时，它会 "moves" 围绕该点旋转，有时会超出屏幕。

 x---    rotate 90 degrees clockwise around X becomes  -----x
 |   |                                                |     |
 |   |                                                 -----
 |   |
  ---

不是很好的图片，但你可以看到如果 x 是一个固定点，视频实际上已经移动了。

无论如何，这很容易修复 - 您缺少翻译（实际上是在输出帧内移动视频的位置）。

使用 CGAffineTranslate 进行实验（按视频的比例），您会看到帧四处移动。

祝你好运！

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