导出时，CALayer 未根据视频上的拖动位置正确设置

Question

我正在尝试使用 CALayer 将文本放在视频上，我有一个可拖动的视图，所以我想根据视频分辨率导出带有精确位置和文本大小的文本的视频，

现在，当我用这个位置导出视频时，结果视频看起来像这样

    let parentLayer = CALayer()
    let videoLayer = CALayer()

    parentLayer.frame = CGRect(x:0, y:0, width:clipVideoTrack.naturalSize.width,height: clipVideoTrack.naturalSize.height)
    videoLayer.frame = CGRect(x:0, y:0, width:clipVideoTrack.naturalSize.width, height:clipVideoTrack.naturalSize.height)


    let backgroundLayer = CALayer()
    backgroundLayer.bounds = CGRect(x: 0, y: 0, width: clipVideoTrack.naturalSize.width, height: clipVideoTrack.naturalSize.height)
    backgroundLayer.position = CGPointMake(clipVideoTrack.naturalSize.width / 2.0, clipVideoTrack.naturalSize.height / 2.0)

    backgroundLayer.addSublayer(supplyView.layer)
    backgroundLayer.masksToBounds = true

    for (index, view) in views.enumerate(){
        var layer = CALayer()
        layer = view.layer
        layer.frame = CGRect(x: supplyView.frame.origin.x, y: supplyView.frame.origin.y, width: supplyView.frame.size.width, height: supplyView.frame.size.height)

        layer.beginTime = CFTimeInterval(Float(startingDurations[index]))
        layer.duration = CFTimeInterval(Float(endingDurations[index]))
        layer.setAffineTransform(view.transform)
        layer.addAnimation(fadeAnimation, forKey: "scale")
        backgroundLayer.addSublayer(layer)
        print(index)
    }
    backgroundLayer.geometryFlipped = true
    parentLayer.addSublayer(backgroundLayer)

    let mainInstruction = AVMutableVideoCompositionInstruction()
    mainInstruction.timeRange = CMTimeRangeMake(kCMTimeZero, mixComposition.duration)
    let videoLayerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: clipVideoTrack)
    let videoAssetTrack = mixComposition.tracksWithMediaType(AVMediaTypeVideo).first

    videoLayerInstruction.setTransform((videoAssetTrack?.preferredTransform)!, atTime: kCMTimeZero)
    videoLayerInstruction.setOpacity(0.0, atTime: videoAsset.duration)
    mainInstruction.layerInstructions = [videoLayerInstruction]

Answer 1

您应该将文本标签的坐标转换为视频帧坐标系。

例如你的 videoLayer 帧是 (0, 0, 200, 200)

真实视频帧可以是(0,0,640,...)

在这种情况下，坐标为 (100,100) 的文本标签将在您的视频中向上和向左移动。标签坐标应为 (300,300) 以保持与视图中相同的位置