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我在 ray wenderlich 中使用视频合并教程。我总是得到一个 90 度旋转的视频。当我添加一些不同的咖啡因旋转代码时，我的视频看不到。你能告诉我我的代码包括 CGAffineTransformMakeRotation。

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
}
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1 回答 1

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CGAffineTransformRotate 围绕一个点进行操作。

当您旋转视频时，它会围绕该点“移动”，包括有时会离开屏幕。 

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

不是一张很好的图片，但您可以看到，如果 x 是一个固定点，则视频实际上已经移动。

无论如何，它很容易修复 - 你错过了翻译（字面意思是在输出帧内移动视频的位置）。

尝试使用 CGAffineTranslate（按视频的比例），您会看到帧四处移动。

祝你好运！

于 2016-02-24T18:00:30.153 回答