AVCaptureStillImageOutput.pngStillImageNSDataRepresentation? - ios

Question

I am working with AVCaptureStillImageOutput for the first time, I save a JPEG image at some point.
Instead of a JPEG image I would like to save a PNG image. What do I need to do for that?
I have those 3 lines of code along the app:
let stillImageOutput = AVCaptureStillImageOutput()
stillImageOutput.outputSettings = [AVVideoCodecKey:AVVideoCodecJPEG]
let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(imageDataSampleBuffer)
Is there a simple way to modify those lines to get what I want?
After browsing the net, it seems like the anser is NO (unless I have not been lucky enough), nevertheless I still believe there must be some good solution.

Answer 1

There is sample code in the AVFoundation Programming Guide that shows how to convert a CMSampleBuffer to a UIImage (under Converting CMSampleBuffer to a UIImage Object). From there, you can use UIImagePNGRepresentation(image) to encode it as PNG data.
Here is a Swift translation of that code:
extension UIImage
{
// Translated from <https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/AVFoundationPG/Articles/06_MediaRepresentations.html#//apple_ref/doc/uid/TP40010188-CH2-SW4>
convenience init?(fromSampleBuffer sampleBuffer: CMSampleBuffer)
{
guard let imageBuffer: CVPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return nil }
if CVPixelBufferLockBaseAddress(imageBuffer, kCVPixelBufferLock_ReadOnly) != kCVReturnSuccess { return nil }
defer { CVPixelBufferUnlockBaseAddress(imageBuffer, kCVPixelBufferLock_ReadOnly) }
let context = CGBitmapContextCreate(
CVPixelBufferGetBaseAddress(imageBuffer),
CVPixelBufferGetWidth(imageBuffer),
CVPixelBufferGetHeight(imageBuffer),
8,
CVPixelBufferGetBytesPerRow(imageBuffer),
CGColorSpaceCreateDeviceRGB(),
CGBitmapInfo.ByteOrder32Little.rawValue | CGImageAlphaInfo.PremultipliedFirst.rawValue)
guard let quartzImage = CGBitmapContextCreateImage(context) else { return nil }
self.init(CGImage: quartzImage)
}
}

Answer 2

Here is Swift 4 version of the above code.
extension UIImage
{
convenience init?(fromSampleBuffer sampleBuffer: CMSampleBuffer)
{
guard let imageBuffer: CVPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return nil }
if CVPixelBufferLockBaseAddress(imageBuffer, .readOnly) != kCVReturnSuccess { return nil }
defer { CVPixelBufferUnlockBaseAddress(imageBuffer, .readOnly) }
let context = CGContext(
data: CVPixelBufferGetBaseAddress(imageBuffer),
width: CVPixelBufferGetWidth(imageBuffer),
height: CVPixelBufferGetHeight(imageBuffer),
bitsPerComponent: 8,
bytesPerRow: CVPixelBufferGetBytesPerRow(imageBuffer),
space: CGColorSpaceCreateDeviceRGB(),
bitmapInfo: CGBitmapInfo.byteOrder32Little.rawValue | CGImageAlphaInfo.premultipliedFirst.rawValue)
guard let quartzImage = context!.makeImage() else { return nil }
self.init(cgImage: quartzImage)
}
}