更新 6：我已经设法完全解决了我的问题，但我仍然想要一个比我猜测的更好的解释，因为如果我不正确，它就不起作用
我一直在尝试在视频上制作精灵表动画，但每次导出视频时，最终结果都是我开始的示例视频。
这是我的代码：
首先我的自定义 CALayer 来处理我自己的精灵表
class SpriteLayer: CALayer {
var frameIndex: Int
override init() {
// Using 0 as a default state
self.frameIndex = 0
super.init()
}
required init?(coder aDecoder: NSCoder) {
self.frameIndex = 0
super.init(coder: aDecoder)
}
override func display() {
let currentFrameIndex = self.frameIndex
if currentFrameIndex == 0 {
return
}
let frameSize = self.contentsRect.size
self.contentsRect = CGRect(x: 0, y: CGFloat(currentFrameIndex - 1) * frameSize.height, width: frameSize.width, height: frameSize.height)
}
override func action(forKey event: String) -> CAAction? {
if event == "contentsRect" {
return nil
}
return super.action(forKey: event)
}
override class func needsDisplay(forKey key: String) -> Bool {
return key == "frameIndex"
}
}
Gif 是一个基本类，没有什么花哨的，而且工作得很好。gif.Strip是一个UIImage表示 gif 的垂直精灵表。
现在是应该导出新视频的方法（它是用于导出的更大类的一部分。
func convertAndExport(to url :URL , completion: @escaping () -> Void ) {
// Get Initial info and make sure our destination is available
self.outputURL = url
let stripCgImage = self.gif.strip!.cgImage!
// This is used to time how long the export took
let start = DispatchTime.now()
do {
try FileManager.default.removeItem(at: outputURL)
} catch {
print("Remove Error: \(error.localizedDescription)")
print(error)
}
// Find and load "sample.mp4" as a AVAsset
let videoPath = Bundle.main.path(forResource: "sample", ofType: "mp4")!
let videoUrl = URL(fileURLWithPath: videoPath)
let videoAsset = AVAsset(url: videoUrl)
// Start a new mutable Composition with the same base video track
let mixComposition = AVMutableComposition()
let compositionVideoTrack = mixComposition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)!
let clipVideoTrack = videoAsset.tracks(withMediaType: .video).first!
do {
try compositionVideoTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAsset.duration), of: clipVideoTrack, at: kCMTimeZero)
} catch {
print("Insert Error: \(error.localizedDescription)")
print(error)
return
}
compositionVideoTrack.preferredTransform = clipVideoTrack.preferredTransform
// Quick access to the video size
let videoSize = clipVideoTrack.naturalSize
// Setup CALayer and it's animation
let aLayer = SpriteLayer()
aLayer.contents = stripCgImage
aLayer.frame = CGRect(x: 0, y: 0, width: videoSize.width, height: videoSize.height)
aLayer.opacity = 1.0
aLayer.masksToBounds = true
aLayer.bounds = CGRect(x: 0, y: 0, width: videoSize.width, height: videoSize.height)
aLayer.contentsRect = CGRect(x: 0, y: 0, width: 1, height: 1.0 / 3.0)
let spriteAnimation = CABasicAnimation(keyPath: "frameIndex")
spriteAnimation.fromValue = 1
spriteAnimation.toValue = 4
spriteAnimation.duration = 2.25
spriteAnimation.repeatCount = .infinity
spriteAnimation.autoreverses = false
spriteAnimation.beginTime = AVCoreAnimationBeginTimeAtZero
aLayer.add(spriteAnimation, forKey: nil)
// Setup Layers for AVVideoCompositionCoreAnimationTool
let parentLayer = CALayer()
let videoLayer = CALayer()
parentLayer.frame = CGRect(x: 0, y: 0, width: videoSize.width, height: videoSize.height)
videoLayer.frame = CGRect(x: 0, y: 0, width: videoSize.width, height: videoSize.height)
parentLayer.addSublayer(videoLayer)
parentLayer.addSublayer(aLayer)
// Create the mutable video composition
let videoComp = AVMutableVideoComposition()
videoComp.renderSize = videoSize
videoComp.frameDuration = CMTimeMake(1, 30)
videoComp.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, in: parentLayer)
// Set the video composition to apply to the composition's video track
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, mixComposition.duration)
let videoTrack = mixComposition.tracks(withMediaType: .video).first!
let layerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack)
instruction.layerInstructions = [layerInstruction]
videoComp.instructions = [instruction]
// Initialize export session
let assetExport = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetPassthrough)!
assetExport.videoComposition = videoComp
assetExport.outputFileType = AVFileType.mp4
assetExport.outputURL = self.outputURL
assetExport.shouldOptimizeForNetworkUse = true
// Export
assetExport.exportAsynchronously {
let status = assetExport.status
switch status {
case .failed:
print("Export Failed")
print("Export Error: \(assetExport.error!.localizedDescription)")
print(assetExport.error!)
case .unknown:
print("Export Unknown")
case .exporting:
print("Export Exporting")
case .waiting:
print("Export Waiting")
case .cancelled:
print("Export Cancelled")
case .completed:
let end = DispatchTime.now()
let nanoTime = end.uptimeNanoseconds - start.uptimeNanoseconds
let timeInterval = Double(nanoTime) / 1_000_000_000
// Function is now over, we can print how long it took
print("Time to generate video: \(timeInterval) seconds")
completion()
}
}
}
编辑：我的代码基于以下链接
- SpriteLayer 以及如何使用它
- 视频中的 CABasicAnimation
- 使用 AVVideoCompositionCoreAnimationTool 和 AVAssetExportSession 保存新视频
更新1：我尝试删除CABasicAnimation我的部分代码并使用我的CALayer但无济于事。我什至无法显示图像。为了进行测试，我尝试在 Xcode Playground 中使用CAKeyframeAnimationon为这个 sprite sheet 设置动画contentsRect，效果很好，所以我认为问题不在于 CABasicAnimation，甚至可能不在于CALayer它本身。我真的可以在这方面使用一些帮助，因为我不明白为什么我什至无法在导出的示例视频上显示图像。
更新 2：为了回应马特的评论，我尝试暂时忘记精灵表，并将其更改为CATextLayer但在我的视频上仍然看不到任何内容（它有深色图像，所以白色文本应该完全可见）
let aLayer = CATextLayer()
aLayer.string = "This is a test"
aLayer.fontSize = videoSize.height / 6
aLayer.alignmentMode = kCAAlignmentCenter
aLayer.foregroundColor = UIColor.white.cgColor
aLayer.bounds = CGRect(x: 0, y: 0, width: videoSize.width, height: videoSize.height / 6)
更新 3：根据马特的要求，我尝试更改parentLayer.addSublayer(aLayer)为，但仍然没有任何改变，但我想了videoLayer.addSublayer(aLayer)很多，因为文档AVVideoCompositionCoreAnimationTool如下
convenience init(postProcessingAsVideoLayer videoLayer: CALayer,
in animationLayer: CALayer)
这意味着我parentLayer的就是它animationLayer，并且可能意味着任何动画都应该在这一层中完成。
更新4：我开始在这里发疯，我现在已经放弃了显示文本或动画图像的想法，我只想以任何可能的方式影响我的视频，所以我改为aLayer：
let aLayer = CALayer()
aLayer.frame = CGRect(x: 0, y: 0, width: videoSize.width, height: videoSize.height)
aLayer.backgroundColor = UIColor.white.cgColor
好吧，这绝对没有任何作用，我仍然可以在 outputUrl 上获得我的示例视频（如果你想“玩”，我开始在操场上用下面的代码测试这个）
import PlaygroundSupport
import UIKit
import Foundation
import AVFoundation
func convertAndExport(to url :URL , completion: @escaping () -> Void ) {
let start = DispatchTime.now()
do {
try FileManager.default.removeItem(at: url)
} catch {
print("Remove Error: \(error.localizedDescription)")
print(error)
}
let videoPath = Bundle.main.path(forResource: "sample", ofType: "mp4")!
let videoUrl = URL(fileURLWithPath: videoPath)
let videoAsset = AVURLAsset(url: videoUrl)
let mixComposition = AVMutableComposition()
let compositionVideoTrack = mixComposition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)!
let clipVideoTrack = videoAsset.tracks(withMediaType: .video).first!
do {
try compositionVideoTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAsset.duration), of: clipVideoTrack, at: kCMTimeZero)
} catch {
print("Insert Error: \(error.localizedDescription)")
print(error)
return
}
compositionVideoTrack.preferredTransform = clipVideoTrack.preferredTransform
let videoSize = clipVideoTrack.naturalSize
print("Video Size Detected: \(videoSize.width) x \(videoSize.height)")
let aLayer = CALayer()
aLayer.frame = CGRect(x: 0, y: 0, width: videoSize.width, height: videoSize.height)
aLayer.backgroundColor = UIColor.white.cgColor
let parentLayer = CALayer()
let videoLayer = CALayer()
parentLayer.frame = CGRect(x: 0, y: 0, width: videoSize.width, height: videoSize.height)
videoLayer.frame = CGRect(x: 0, y: 0, width: videoSize.width, height: videoSize.height)
parentLayer.addSublayer(videoLayer)
parentLayer.addSublayer(aLayer)
aLayer.setNeedsDisplay()
let videoComp = AVMutableVideoComposition()
videoComp.renderSize = videoSize
videoComp.frameDuration = CMTimeMake(1, 30)
videoComp.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videoLayer, in: parentLayer)
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, mixComposition.duration)
let videoTrack = mixComposition.tracks(withMediaType: .video).first!
let layerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack)
instruction.layerInstructions = [layerInstruction]
videoComp.instructions = [instruction]
let assetExport = AVAssetExportSession(asset: mixComposition, presetName: AVAssetExportPresetPassthrough)!
assetExport.videoComposition = videoComp
assetExport.outputFileType = AVFileType.mp4
assetExport.outputURL = url
assetExport.shouldOptimizeForNetworkUse = true
assetExport.exportAsynchronously {
let status = assetExport.status
switch status {
case .failed:
print("Export Failed")
print("Export Error: \(assetExport.error!.localizedDescription)")
print(assetExport.error!)
case .unknown:
print("Export Unknown")
case .exporting:
print("Export Exporting")
case .waiting:
print("Export Waiting")
case .cancelled:
print("Export Cancelled")
case .completed:
let end = DispatchTime.now()
let nanoTime = end.uptimeNanoseconds - start.uptimeNanoseconds
let timeInterval = Double(nanoTime) / 1_000_000_000
print("Time to generate video: \(timeInterval) seconds")
completion()
}
}
}
let outputUrl = FileManager.default.temporaryDirectory.appendingPathComponent("test.mp4")
convertAndExport(to: outputUrl) {
print(outputUrl)
}
请有人帮我理解我做错了什么......
更新 5：我正在运行除了 iPad Air 2（所以没有模拟器）的游乐场测试之外的所有内容，因为我使用相机拍照，然后将它们拼接成一个精灵表，然后我计划在我将通过电子邮件发送的视频上制作动画。我开始做 Playground 测试，因为 iPad 上的每个测试都要求我完成整个应用程序周期（倒计时、照片、表单、电子邮件发送/接收）