LottieInVideo

Render Lottie in video by AVFoundation

PAG vs Lottie

渲染矢量动画到视频里面，PAG更适合做这件事。
Rendering vector animation in video, PAG is best for this job than lottie.

Lottie 3.1.0

分支 master 使用的 Lottie 版本

Lottie 2.5.2

分支 lottie-2.5.2 在 Lottie 2.5.2 版本，Lottie 重构了生成动画的方案。新的方案使用了各种插值器（Interpolate）来生成每一帧的贝塞尔曲线/点等等，最后用CoreGraphics来画。所以我们可以对layer做截图，然后把生成的图片和视频图片进行叠加。

Lottie 1.0.4

在 Lottie 1.0.4 版本，Lottie 是基于 CAAnimation 实现的动画，那时候合成到视频中需要借助 AVVideoComposition 的 animationTool。

    let instruction = AVMutableVideoCompositionInstruction()
    instruction.timeRange = CMTimeRange(start: CMTime.zero, duration: asset.duration)
    instruction.layerInstructions = [layerInstruction]
    videoComposition.instructions = [instruction]
    if let animationLayer = createStickerLayer(in: renderSize) {
        let parentLayer = CALayer()
        let videoLayer = CALayer()
        let contentLayer = CALayer()
        parentLayer.frame = CGRect(x: 0, y: 0, width: renderSize.width, height: renderSize.height)
        videoLayer.frame = CGRect(x: 0, y: 0, width: renderSize.width, height: renderSize.height)
        contentLayer.frame = CGRect(x: 0, y: 0, width: renderSize.width, height: renderSize.height)
        contentLayer.addSublayer(animationLayer)
        contentLayer.isGeometryFlipped = true
        parentLayer.addSublayer(videoLayer)
        parentLayer.addSublayer(contentLayer)
        videoComposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, in: parentLayer)
    }

    private func createStickerLayer(in size: CGSize) -> CALayer? {
        guard let sticker = sticker else { return nil }
        let layer = CALayer()
        layer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
        do {
            let animationData = try Data(contentsOf: URL(fileURLWithPath: sticker.url))
            if let animationJSON = try JSONSerialization.jsonObject(with: animationData, options: JSONSerialization.ReadingOptions(rawValue: UInt(0))) as? Dictionary<String, Any> {
                let animationLayer = LOTAnimationLayer.animation(fromJSON: animationJSON, customData: [], loop: false)!
                animationLayer.bounds = sticker.bounds(containerBounds: layer.bounds)
                animationLayer.position = sticker.center(containerBounds: layer.bounds)
                animationLayer.setAffineTransform(sticker.transform)
                animationLayer.beginTime = sticker.range.start.seconds
                animationLayer.duration = sticker.range.duration.seconds
                animationLayer.speed = sticker.speed
                layer.addSublayer(animationLayer)
            }
        } catch let e {
            print(e)
        }
        return layer
    }