Vertically stitches frames of a GIF into a single image

Gif stitcher

let image = #imageLiteral(resourceName: "Arrow.gif")

let imageRep = image.representations.first! as! NSBitmapImageRep
let numFrames = imageRep.value(forProperty: NSImageFrameCount) as! Int
let numLoops = imageRep.value(forProperty: NSImageCurrentFrameDuration) as! Float

var cgImages = [CGImage]()
var nsImages = [NSImage]()
var size = NSSize()
for frame in 0..<numFrames {
	let nsNumber = NSNumber(value: frame)
	imageRep.setProperty(NSImageCurrentFrame, withValue: nsNumber)
	print(imageRep.value(forProperty: NSImageCurrentFrame) as Any)
	
	let cgImage = imageRep.cgImage!
	cgImages.append(cgImage)
	nsImages.append(NSImage(cgImage: cgImage, size: imageRep.size))
	
	size = imageRep.size
}
cgImages
nsImages


let typicalImage = nsImages.first!
let typicalImageRep = typicalImage.representations.first!
let typicalCGImage = cgImages.first!

let typicalHeight = Int(typicalImageRep.size.height)
let totalHeight = typicalHeight * nsImages.count
let typicalWidth = Int(typicalImageRep.size.width)
let bitsPerComponent = typicalImageRep.bitsPerSample

let colorSpace = typicalCGImage.colorSpace!
CGImageAlphaInfo.noneSkipLast
let bitmapInfo = typicalCGImage.bitmapInfo.rawValue | typicalCGImage.alphaInfo.rawValue

let ctx = CGContext(data: nil, width: typicalWidth, height: totalHeight,
                    bitsPerComponent: bitsPerComponent, bytesPerRow: 0,
                    space: colorSpace, bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue)!

//let ctx = CGContext(data: nil, width: width, height: totalHeight,
//                    bitsPerComponent: bitsPerComponent, bytesPerRow: 0,
//                    space: colorSpace, bitmapInfo: bitmapInfo)!
var steps = [NSImage]()
for (index, image) in cgImages.enumerated() {
	let y = totalHeight - typicalHeight - index * typicalHeight
	ctx.draw(image, in: CGRect.init(x: 0, y: y, width: typicalWidth, height: typicalHeight))
	let cgImage = ctx.makeImage()!
	let i = NSImage(cgImage: cgImage, size: NSSize(width: cgImage.width, height: cgImage.height))
	steps.append(i)
}

steps

let cgImage = ctx.makeImage()!
NSImage(cgImage: cgImage, size: NSSize(width: cgImage.width, height: cgImage.height))