从AVAssetExportSession导出视频时，CATextlayer字体大小不变

Question

我正在使用CATextLayer在视频上添加文本。 但是在导出过程完成后，文本大小不会随框架位置而变化。 字体大小在日志中打印，但CATextLayer字体大小不变。 这是我完成的代码。

let mainCompositionInst = AVMutableVideoComposition()
    var naturalSize = CGSize()
    naturalSize = CGSize(width: (videoAssetTrack?.naturalSize.width)!, height:(videoAssetTrack?.naturalSize.height)!)
    var renderWidth = CGFloat()
    var renderHeight = CGFloat()

    renderWidth = naturalSize.width
    renderHeight = naturalSize.height

    mainCompositionInst.renderSize = CGSize(width: renderWidth, height: renderHeight)
    mainCompositionInst.instructions = [mainInstruction]
    mainCompositionInst.frameDuration = CMTimeMake(1, 30)

let myAttributes = [
        NSFontAttributeName: UIFont(name: "HelveticaNeue-Thin", size: 30)!, // font
        NSForegroundColorAttributeName: UIColor.white                   // text color
    ]
    let myAttributedString = NSAttributedString(string: "Title", attributes: myAttributes )

    let titleLayer = CATextLayer()
    titleLayer.string = myAttributedString

    titleLayer.frame = CGRect(x: (dragView?.frame.origin.x)!, y: (dragView?.frame.origin.y)!, width: (dragView?.frame.size.width)!, height: (dragView?.frame.height)!)
    titleLayer.shadowOpacity = 0.5
    titleLayer.isWrapped = true


    print("Font Size \(String(describing: titleLayer.fontSize))")
    let overlayLayer = CALayer()
    overlayLayer.addSublayer(titleLayer)
    overlayLayer.frame = CGRect(x: 0, y: 0, width: naturalSize.width, height: naturalSize.height)
    overlayLayer.masksToBounds = true

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


    parentLayer.addSublayer(videoLayer)
    parentLayer.addSublayer(overlayLayer)

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

Answer 1

仅添加了一行代码，代码可以正常工作titleLayer.shouldRasterize = true