我正在学习AVFoundation，我在尝试使用Swift 3保存带有覆盖图像的视频时遇到了问题。使用
AVMutableComposition，我可以将图像添加到视频中，但是视频会放大并且无法约束为拍摄时的竖屏大小。我已经尝试过：
- 通过
AVAssetTrack设置自然大小。 - 在
AVMutableVideoComposition renderFrame中将视频限制为竖屏大小。 - 将新视频边界锁定为录制视频的宽度和高度。
func processVideoWithWatermark(video: AVURLAsset, watermark: UIImage, completion: @escaping (Bool) -> Void) {
let composition = AVMutableComposition()
let asset = AVURLAsset(url: video.url, options: nil)
let track = asset.tracks(withMediaType: AVMediaTypeVideo)
let videoTrack:AVAssetTrack = track[0] as AVAssetTrack
let timerange = CMTimeRangeMake(kCMTimeZero, asset.duration)
let compositionVideoTrack:AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
do {
try compositionVideoTrack.insertTimeRange(timerange, of: videoTrack, at: kCMTimeZero)
compositionVideoTrack.preferredTransform = videoTrack.preferredTransform
} catch {
print(error)
}
// let compositionAudioTrack:AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: CMPersistentTrackID())
//
// for audioTrack in asset.tracks(withMediaType: AVMediaTypeAudio) {
// do {
// try compositionAudioTrack.insertTimeRange(audioTrack.timeRange, of: audioTrack, at: kCMTimeZero)
// } catch {
// print(error)
// }
//
// }
//
let size = videoTrack.naturalSize
let watermark = watermark.cgImage
let watermarklayer = CALayer()
watermarklayer.contents = watermark
watermarklayer.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)
watermarklayer.opacity = 1
let videolayer = CALayer()
videolayer.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)
let parentlayer = CALayer()
parentlayer.frame = CGRect(x: 0, y: 0, width: size.width, height: size.height)
parentlayer.addSublayer(videolayer)
parentlayer.addSublayer(watermarklayer)
let layercomposition = AVMutableVideoComposition()
layercomposition.frameDuration = CMTimeMake(1, 30)
layercomposition.renderSize = CGSize(width: screenWidth, height: screenHeight)
layercomposition.renderScale = 1.0
layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videolayer, in: parentlayer)
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, composition.duration)
let videotrack = composition.tracks(withMediaType: AVMediaTypeVideo)[0] as AVAssetTrack
let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videotrack)
layerinstruction.setTransform(videoTrack.preferredTransform, at: kCMTimeZero)
instruction.layerInstructions = [layerinstruction]
layercomposition.instructions = [instruction]
let filePath = NSTemporaryDirectory() + self.fileName()
let movieUrl = URL(fileURLWithPath: filePath)
guard let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetHighestQuality) else {return}
assetExport.videoComposition = layercomposition
assetExport.outputFileType = AVFileTypeMPEG4
assetExport.outputURL = movieUrl
assetExport.exportAsynchronously(completionHandler: {
switch assetExport.status {
case .completed:
print("success")
print(video.url)
self.saveVideoToUserLibrary(fileURL: movieUrl, completion: { (success, error) in
if success {
completion(true)
} else {
completion(false)
}
})
break
case .cancelled:
print("cancelled")
break
case .exporting:
print("exporting")
break
case .failed:
print(video.url)
print("failed: \(assetExport.error!)")
break
case .unknown:
print("unknown")
break
case .waiting:
print("waiting")
break
}
})
}