swift - 如何制作方形视频？

Question

尝试通过animationTool制作方形视频。 请参阅下面的代码。视频放大了(/image/HscTk.jpg)，我该如何修复？

let exportSession = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetHighestQuality)
        let strFilePath: String = generateMergedVideoFilePath()
        try? FileManager.default.removeItem(atPath: strFilePath)
        exportSession?.outputURL = URL(fileURLWithPath: strFilePath)
        exportSession?.outputFileType = .mp4
        exportSession?.shouldOptimizeForNetworkUse = true
        let mutableVideoComposition = AVMutableVideoComposition(propertiesOf: composition)
        mutableVideoComposition.instructions = instructions
        mutableVideoComposition.frameDuration = CMTimeMake(value: 1, timescale: 30)
        mutableVideoComposition.renderSize = CGSize(width: 1080, height: 1080)

        let parentLayer = CALayer()
        parentLayer.frame = CGRect(x: 0, y: 0, width: 1080, height: 1080)
        let videoLayer = CALayer()
        videoLayer.frame.size = videoSize
        videoLayer.position = parentLayer.position
        videoLayer.contentsGravity = .resizeAspectFill
        parentLayer.addSublayer(videoLayer)


        mutableVideoComposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, in: parentLayer)

Answer 1

mutableVideoComposition.renderSize = CGSize (width: 1080, height: 1080)

使用此分辨率，它会获取相对于顶点的图像，因此我将变换向上移动

let coeConst = videoAssetWidth/videoAssetHeight
transform.translatedBy(x: -(videoAssetHeight-videoAssetHeight*coeConst)/2, y: 0)