AVExportSession中CALayer中的视频重力
AVExportSession中CALayer中的视频重力
提问于 2017-06-10 16:05:26
我的应用程序首先录制一段视频，然后添加一些效果，然后使用AVExportSession导出输出。
首先，视频录制过程中的视频重力问题，通过将AVCaptureVideoPreviewLayer内部的videoGravity属性更改为AVLayerVideoGravityResizeAspectFill来解决。
第二个问题是显示录制的视频，该问题已通过将AVPlayerLayer内的VideoGravity属性更改为AVLayerVideoGravityResizeAspectFill来解决
但是，现在的问题是，当我想用AVExportSession添加一些效果后导出视频时，又出现了一些视频重力问题。即使在CALayer中更改contentsGravity属性也不会影响输出。我应该提一下，这个问题在iPad中是显而易见的。
下面是我想要在添加一些效果之前显示视频的图像：
正如你所看到的，我的指尖在屏幕的顶部(因为我已经修复了应用程序内部图层中的重力问题)
但导出并保存到图库后，我看到的内容如下所示：
我知道问题出在地心引力上，但我不知道如何解决它。我不知道在录制时是否应该对视频进行任何更改，或者在导出时更改以下代码：
let composition = AVMutableComposition()
let asset = AVURLAsset(url: videoUrl, options: nil)
let tracks = asset.tracks(withMediaType : AVMediaTypeVideo)
let videoTrack:AVAssetTrack = tracks[0] as AVAssetTrack
let timerange = CMTimeRangeMake(kCMTimeZero, asset.duration)
let viewSize = parentView.bounds.size
let trackSize = videoTrack.naturalSize
let compositionVideoTrack:AVMutableCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: CMPersistentTrackID())
do {
try compositionVideoTrack.insertTimeRange(timerange, of: videoTrack, at: kCMTimeZero)
} 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 videolayer = CALayer()
videolayer.frame.size = viewSize
videolayer.contentsGravity = kCAGravityResizeAspectFill
let parentlayer = CALayer()
parentlayer.frame.size = viewSize
parentlayer.contentsGravity = kCAGravityResizeAspectFill
parentlayer.addSublayer(videolayer)
let layercomposition = AVMutableVideoComposition()
layercomposition.frameDuration = CMTimeMake(1, 30)
layercomposition.renderSize = viewSize
layercomposition.animationTool = AVVideoCompositionCoreAnimationTool(postProcessingAsVideoLayer: videolayer, in: parentlayer)
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration)
let videotrack = composition.tracks(withMediaType: AVMediaTypeVideo)[0] as AVAssetTrack
let layerinstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videotrack)
let trackTransform = videoTrack.preferredTransform
let xScale = viewSize.height / trackSize.width
let yScale = viewSize.width / trackSize.height
var exportTransform : CGAffineTransform!
if (getVideoOrientation(transform: videoTrack.preferredTransform).1 == .up) {
exportTransform = videoTrack.preferredTransform.translatedBy(x: trackTransform.ty * -1 , y: 0).scaledBy(x: xScale , y: yScale)
} else {
exportTransform = CGAffineTransform.init(translationX: viewSize.width, y: 0).rotated(by: .pi/2).scaledBy(x: xScale, y: yScale)
}
layerinstruction.setTransform(exportTransform, at: kCMTimeZero)
instruction.layerInstructions = [layerinstruction]
layercomposition.instructions = [instruction]
let filePath = FileHelper.getVideoTimeStampName()
let exportedUrl = URL(fileURLWithPath: filePath)
guard let assetExport = AVAssetExportSession(asset: composition, presetName:AVAssetExportPresetHighestQuality) else {delegate?.exportFinished(status: .failed, outputUrl: exportedUrl); return}
assetExport.videoComposition = layercomposition
assetExport.outputFileType = AVFileTypeMPEG4
assetExport.outputURL = exportedUrl
assetExport.exportAsynchronously(completionHandler: {
switch assetExport.status {
case .completed:
print("video exported successfully")
self.delegate?.exportFinished(status: .completed, outputUrl: exportedUrl)
break
case .failed:
self.delegate?.exportFinished(status: .failed, outputUrl: exportedUrl)
print("exporting video failed: \(String(describing: assetExport.error))")
break
default :
print("the video export status is \(assetExport.status)")
self.delegate?.exportFinished(status: assetExport.status, outputUrl: exportedUrl)
break
}
})如果有人能帮上忙，我将不胜感激。
回答 1
Stack Overflow用户
发布于 2017-06-14 17:26:01
如果您使用的是AVLayerVideoGravityResizeAspectFill，视频捕获屏幕将自动调整为CALayer。因此，实际发生的情况是，摄像机实际上捕捉到了您提供的第二张图像。您可以通过以下步骤解决此问题：
- 获取图像作为UIImage
- 裁剪与您正在使用的CALayer大小相同的图像
- 将裁剪后的图像上传到服务器，显示给用户，等等。
要裁剪图像，您可以使用以下命令：
extension UIImage {
func crop(to:CGSize) -> UIImage {
guard let cgimage = self.cgImage else { return self }
let contextImage: UIImage = UIImage(cgImage: cgimage)
let contextSize: CGSize = contextImage.size
//Set to square
var posX: CGFloat = 0.0
var posY: CGFloat = 0.0
let cropAspect: CGFloat = to.width / to.height
var cropWidth: CGFloat = to.width
var cropHeight: CGFloat = to.height
if to.width > to.height { //Landscape
cropWidth = contextSize.width
cropHeight = contextSize.width / cropAspect
posY = (contextSize.height - cropHeight) / 2
} else if to.width < to.height { //Portrait
cropHeight = contextSize.height
cropWidth = contextSize.height * cropAspect
posX = (contextSize.width - cropWidth) / 2
} else { //Square
if contextSize.width >= contextSize.height { //Square on landscape (or square)
cropHeight = contextSize.height
cropWidth = contextSize.height * cropAspect
posX = (contextSize.width - cropWidth) / 2
}else{ //Square on portrait
cropWidth = contextSize.width
cropHeight = contextSize.width / cropAspect
posY = (contextSize.height - cropHeight) / 2
}
}
let rect: CGRect = CGRect(x: posX, y: posY, width: cropWidth, height: cropHeight)
// Create bitmap image from context using the rect
let imageRef: CGImage = contextImage.cgImage!.cropping(to: rect)!
// Create a new image based on the imageRef and rotate back to the original orientation
let cropped: UIImage = UIImage(cgImage: imageRef, scale: self.scale, orientation: self.imageOrientation)
UIGraphicsBeginImageContextWithOptions(to, true, self.scale)
cropped.draw(in: CGRect(x: 0, y: 0, width: to.width, height: to.height))
let resized = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return resized!
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/44471040
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