How to get image Data properly?

Question

I'm trying to take photo and return image data as return type of function. AVFoundation takes picture asynchronous, and my function returns before it's finished, so I get empty bytes.

I tried calling takePicture() with waiting, as said in this reply Waiting until the task finishes but it just freezes UI.

func takePicture() -> Data {

    var imageData: Data?

        self.stillImageOutput?.captureStillImageAsynchronously(from: videoConnection!, completionHandler: { (imageDataBuffer, error) in

            if let result = AVCapturePhotoOutput.jpegPhotoDataRepresentation(forJPEGSampleBuffer: imageDataBuffer!, previewPhotoSampleBuffer: imageDataBuffer!) {
                imageData = result
            }

            // Removing sessions and stop running
        })

    return imageData!
}

Possible duplicate of [Wait for async function return value in swift](https://stackoverflow.com/questions/34861337/wait-for-async-function-return-value-in-swift) — Cristik, Sep 29 '19 at 19:24

score 1 · Accepted Answer · answered Sep 29 '19 at 12:43

You need a completion

func takePicture(completion:@escaping(Data?) -> ()) {
    self.stillImageOutput?.captureStillImageAsynchronously(from: videoConnection!, completionHandler: { (imageDataBuffer, error) in
        if let result = AVCapturePhotoOutput.jpegPhotoDataRepresentation(forJPEGSampleBuffer: imageDataBuffer!, previewPhotoSampleBuffer: imageDataBuffer!) {
            completion(result)
        }
        else {
              completion(nil)
        }
    })
}

How to get image Data properly?

1 Answers1