How to add transitions to set images exported as video in Swift - swift

Question

I am making an app which has functionality for Transitions like example-video should play from top to bottom or from left to right transitions effect.I am able to generate video from set of image array in swift 3.0 but i am not getting how to add transitions.
I got the code from this answer How do I export UIImage array as a movie?
I am using like this working fine only problem to get trasnitions
func writeImagesAsMovie(allImages: [UIImage], videoPath: String, videoSize: CGSize, videoFPS: Int32) {
// Create AVAssetWriter to write video
guard let assetWriter = createAssetWriter(videoPath, size: videoSize) else {
print("Error converting images to video: AVAssetWriter not created")
return
}
// If here, AVAssetWriter exists so create AVAssetWriterInputPixelBufferAdaptor
let writerInput = assetWriter.inputs.filter{ $0.mediaType == AVMediaTypeVideo }.first!
let sourceBufferAttributes : [String : AnyObject] = [
kCVPixelBufferPixelFormatTypeKey as String : Int(kCVPixelFormatType_32ARGB) as AnyObject,
kCVPixelBufferWidthKey as String : videoSize.width as AnyObject,
kCVPixelBufferHeightKey as String : videoSize.height as AnyObject,
]
let pixelBufferAdaptor = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: writerInput, sourcePixelBufferAttributes: sourceBufferAttributes)
// Start writing session
assetWriter.startWriting()
assetWriter.startSession(atSourceTime: kCMTimeZero)
if (pixelBufferAdaptor.pixelBufferPool == nil) {
print("Error converting images to video: pixelBufferPool nil after starting session")
return
}
// -- Create queue for <requestMediaDataWhenReadyOnQueue>
let mediaQueue = DispatchQueue(label: "mediaInputQueue", attributes: [])
// -- Set video parameters
let frameDuration = CMTimeMake(1, videoFPS)
var frameCount = 0
// -- Add images to video
let numImages = allImages.count
writerInput.requestMediaDataWhenReady(on: mediaQueue, using: { () -> Void in
// Append unadded images to video but only while input ready
while (writerInput.isReadyForMoreMediaData && frameCount < numImages) {
let lastFrameTime = CMTimeMake(Int64(frameCount), videoFPS)
let presentationTime = frameCount == 0 ? lastFrameTime : CMTimeAdd(lastFrameTime, frameDuration)
if !self.appendPixelBufferForImageAtURL(image: allImages[frameCount], pixelBufferAdaptor: pixelBufferAdaptor, presentationTime: presentationTime) {
print("Error converting images to video: AVAssetWriterInputPixelBufferAdapter failed to append pixel buffer")
return
}
frameCount += 1
}
// No more images to add? End video.
if (frameCount >= numImages) {
writerInput.markAsFinished()
assetWriter.finishWriting {
if (assetWriter.error != nil) {
print("Error converting images to video: \(String(describing: assetWriter.error))")
} else {
print("Converted images to movie # \(videoPath)")
}
}
}
})
}
func createAssetWriter(_ path: String, size: CGSize) -> AVAssetWriter? {
// Convert <path> to NSURL object
let pathURL = URL(fileURLWithPath: path)
// Return new asset writer or nil
do {
// Create asset writer
let newWriter = try AVAssetWriter(outputURL: pathURL, fileType: AVFileTypeMPEG4)
// Define settings for video input
let videoSettings: [String : AnyObject] = [
AVVideoCodecKey : AVVideoCodecH264 as AnyObject,
AVVideoWidthKey : size.width as AnyObject,
AVVideoHeightKey : size.height as AnyObject,
]
// Add video input to writer
let assetWriterVideoInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: videoSettings)
newWriter.add(assetWriterVideoInput)
// Return writer
print("Created asset writer for \(size.width)x\(size.height) video")
return newWriter
} catch {
print("Error creating asset writer: \(error)")
return nil
}
}
func appendPixelBufferForImageAtURL(image: UIImage, pixelBufferAdaptor: AVAssetWriterInputPixelBufferAdaptor, presentationTime: CMTime) -> Bool {
var appendSucceeded = false
autoreleasepool {
if let pixelBufferPool = pixelBufferAdaptor.pixelBufferPool {
let pixelBufferPointer = UnsafeMutablePointer<CVPixelBuffer?>.allocate(capacity:1)
let status: CVReturn = CVPixelBufferPoolCreatePixelBuffer(
kCFAllocatorDefault,
pixelBufferPool,
pixelBufferPointer
)
if let pixelBuffer = pixelBufferPointer.pointee , status == 0 {
fillPixelBufferFromImage(image: image, pixelBuffer: pixelBuffer)
appendSucceeded = pixelBufferAdaptor.append(pixelBuffer, withPresentationTime: presentationTime)
pixelBufferPointer.deinitialize()
} else {
NSLog("Error: Failed to allocate pixel buffer from pool")
}
pixelBufferPointer.deallocate(capacity: 1)
}
}
return appendSucceeded
}
func fillPixelBufferFromImage(image: UIImage, pixelBuffer: CVPixelBuffer) {
CVPixelBufferLockBaseAddress(pixelBuffer, CVPixelBufferLockFlags(rawValue: CVOptionFlags(0)))
let pixelData = CVPixelBufferGetBaseAddress(pixelBuffer)
let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
// Create CGBitmapContext
let context = CGContext(
data: pixelData,
width: Int(image.size.width),
height: Int(image.size.height),
bitsPerComponent: 8,
bytesPerRow: CVPixelBufferGetBytesPerRow(pixelBuffer),
space: rgbColorSpace,
bitmapInfo: CGImageAlphaInfo.premultipliedFirst.rawValue
)
// Draw image into context
context?.draw(image .cgImage!, in: CGRect(x: 0.0,y: 0.0,width: image.size.width,height: image .size.height))
CVPixelBufferUnlockBaseAddress(pixelBuffer, CVPixelBufferLockFlags(rawValue: 0))
}