夫特：方形視頻組合

Question

我下面下面的代碼爲正方形視頻組合

func completeWithVideoAtURL(input: NSURL) { 
    let asset = AVAsset(url: input as URL) 
    let output = NSURL(fileURLWithPath: NSHomeDirectory() + "/Documents/Video.mp4") 

    let session = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetMediumQuality)! 
    session.videoComposition = self.squareVideoCompositionForAsset(asset: asset) 
    session.outputURL = output as URL 
    session.outputFileType = AVFileTypeMPEG4 
    session.shouldOptimizeForNetworkUse = true   
    session.exportAsynchronously(completionHandler: {() -> Void in 
     DispatchQueue.main.async(execute: {() -> Void in 
      // do something with the output 
      print("\(output)") 
      PHPhotoLibrary.shared().performChanges({ 
       PHAssetChangeRequest.creationRequestForAssetFromVideo(atFileURL: output as URL) 
      }) { saved, error in 
       if saved { 
        print("saved to gallery") 
       } 
      } 
     }) 
    }) 
} 

func squareVideoCompositionForAsset(asset: AVAsset) -> AVVideoComposition { 
    let track = asset.tracks(withMediaType: AVMediaTypeVideo)[0] 
    let length = max(track.naturalSize.width, track.naturalSize.height) 

    var transform = track.preferredTransform 

    let size = track.naturalSize 
    let scale: CGFloat = (transform.a == -1 && transform.b == 0 && transform.c == 0 && transform.d == -1) ? -1 : 1 // check for inversion 

    transform = transform.translatedBy(x: scale * -(size.width - length)/2, y: scale * -(size.height - length)/2) 

    let transformer = AVMutableVideoCompositionLayerInstruction(assetTrack: track) 
    transformer.setTransform(transform, at: kCMTimeZero) 

    let instruction = AVMutableVideoCompositionInstruction() 
    instruction.timeRange = CMTimeRange(start: kCMTimeZero, duration: kCMTimePositiveInfinity) 
    instruction.layerInstructions = [transformer] 

    let composition = AVMutableVideoComposition() 
    composition.frameDuration = CMTime(value: 1, timescale: 30) 
    composition.renderSize = CGSize(width: length, height: length) 
    composition.instructions = [instruction] 

    return composition 
} 

從squareVideoCompositionForAsset（）函數I採取最大值長度 track.naturalSize之間。寬度 & track.naturalSize.height因爲我不想裁剪視頻的任何部分部分。如果我取最小值，對於縱向視頻，它會剪切視頻的較低部分，對於橫向視頻，它會剪切一些左邊的&視頻的右側部分。

• 對於景觀的視頻，輸出是正常

• 但對於人像視頻輸出就像下面的圖片

韋迪o得到左側。視頻是否可以居中？任何援助將是偉大的，並遺憾長時間的解釋。

Answer 1

代替該線

設規模：CGFloat的=（transform.a == -1 & & transform.b == 0 & & transform.c == 0 & & transform.d = = -1）？ -1：1

我只是用這個

var scale = CGFloat() 
    if (transform.a == 0 && transform.b == 1 && transform.c == -1 && transform.d == 0) { 
     scale = -1 
    } 
    else if (transform.a == 0 && transform.b == -1 && transform.c == 1 && transform.d == 0) { 
     scale = -1 
    } 
    else if (transform.a == 1 && transform.b == 0 && transform.c == 0 && transform.d == 1) { 
     scale = 1 
    } 
    else if (transform.a == -1 && transform.b == 0 && transform.c == 0 && transform.d == -1) { 
     scale = 1 
    } 

和它的工作就像一個魅力