Question

我尝试通过AVExportSession为我的自定义CALayer导出动画，请找到以下设置：

class CustomAnimatable: CALayer
{
    @NSManaged var brightness: CGFloat

    override init(layer: Any) {
        super.init(layer: layer);

        if let l = layer as? CustomAnimatable {
            self.brightness = l.brightness;
        }
    }

    override func action(forKey event: String) -> CAAction?
    {
        if event == "brightness" {
            let animation = CABasicAnimation(keyPath: event);
            animation.fromValue = presentation()?.brightness ?? self.brightness;
            return animation;
        }

        return super.action(forKey: event);
    }

    override class func needsDisplay(forKey key: String) -> Bool
    {
        if key == "brightness" {
            return true;
        }

        return super.needsDisplay(forKey: key);
    }

    override func display()
    {
        print("\(self) \(presentation()?.brightness) \(self.brightness)")
    }
}

这是预先设置的导出会话：

func render()
{
     ......

    let parentLayer = CALayer();
    let videoLayer = CALayer();
    let animationLayer = CustomAnimatable()

    parentLayer.frame = frame;
    videoLayer.frame = frame;
    animationLayer.frame = frame;

    parentLayer.addSublayer(videoLayer);
    parentLayer.addSublayer(animationLayer);

    CATransaction.begin()
    CATransaction.setAnimationDuration(2.2);
    CATransaction.setDisableActions(true);
    CATransaction.setAnimationTimingFunction(CAMediaTimingFunction(name: kCAMediaTimingFunctionLinear))

    let anim = CABasicAnimation(keyPath: "brightness");

    anim.fromValue = 1.0;
    anim.fillMode = kCAFillModeBoth;
    anim.beginTime = AVCoreAnimationBeginTimeAtZero;
    anim.repeatCount = 1;
    anim.toValue = 0.0;
    anim.isRemovedOnCompletion = false;

    animationLayer.add(anim, forKey: "anim")

    CATransaction.commit()


    let videoComposition = AVMutableVideoComposition();

    videoComposition.renderSize = CGSize(width: width, height: height);
    videoComposition.instructions = [mainInstruction];
    videoComposition.frameDuration = CMTimeMake(1, 30);
    videoComposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, in: parentLayer);

     ....
}

问题是生成的视频中的brightness值从1变为0而没有动画。如果我尝试为CALayer的原生属性设置动画，例如opacity - 导出的动画视频非常精细，不透明度从1平滑变为0。

我是否为自定义属性做错了？

我考虑过的事情：

将显式动画包装到CATransaction以禁用隐式操作
根据＆＃34; Editing Media with AV Foundation＆＃34;将动画开始时间设置为AVCoreAnimationBeginTimeAtZero和isRemovedOnCompletion为false session（Core Animation Gotchas部分）

我对本机CALayer属性动画很好的事实感到有点困惑，因此导出会话设置似乎是正确的。

除此之外，如果我将自定义图层添加到视图并为brightness属性设置动画 - 它也可以生动。所以这个问题似乎特定于使用AVExportSession渲染自定义属性动画。

Answer 1

我不完全确定您在videoLayer中添加了animationLayer和parentLayer?课程的原因。

parentLayer.addSublayer(videoLayer);
parentLayer.addSublayer(animationLayer);

使用以下代码希望对您有所帮助！

parentLayer.addSublayer(videoLayer);
videoLayer.addSublayer(animationLayer);

通过AVExportSession导出带有隐式动画的CALayer

1 个答案: