iPad capturing 16:9 photos - objective-c

Question

I am building a prototype app on iOS, and I’m cannibalizing some Apple sample code to do it (thin ice, I know—this code uses goto statements :\ ). I am using the AVCam project from Session 520 - What's New in Camera Capture. I don’t need video capture capability, just still photos.
The device inputs and outputs are set up thusly:
// Init the device inputs
AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self backFacingCamera] error:nil];
AVCaptureDeviceInput *newAudioInput = [[AVCaptureDeviceInput alloc] initWithDevice:[self audioDevice] error:nil];
// Setup the still image file output
AVCaptureStillImageOutput *newStillImageOutput = [[AVCaptureStillImageOutput alloc] init];
NSDictionary *outputSettings = #{AVVideoCodecKey: AVVideoCodecJPEG};
[newStillImageOutput setOutputSettings:outputSettings];
// Create session (use default AVCaptureSessionPresetHigh)
AVCaptureSession *newCaptureSession = [[AVCaptureSession alloc] init];
// Add inputs and output to the capture session
if ([newCaptureSession canAddInput:newVideoInput]) {
[newCaptureSession addInput:newVideoInput];
}
if ([newCaptureSession canAddInput:newAudioInput]) {
[newCaptureSession addInput:newAudioInput];
}
if ([newCaptureSession canAddOutput:newStillImageOutput]) {
[newCaptureSession addOutput:newStillImageOutput];
}
[self setStillImageOutput:newStillImageOutput];
[self setVideoInput:newVideoInput];
[self setAudioInput:newAudioInput];
[self setSession:newCaptureSession];
And here is the method that’s called when I tap the shutter button:
- (void) captureStillImage
{
AVCaptureConnection *stillImageConnection = [[self stillImageOutput] connectionWithMediaType:AVMediaTypeVideo];
if ([stillImageConnection isVideoOrientationSupported])
[stillImageConnection setVideoOrientation:orientation];
[[self stillImageOutput]
captureStillImageAsynchronouslyFromConnection:stillImageConnection
completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
ALAssetsLibraryWriteImageCompletionBlock completionBlock = ^(NSURL *assetURL, NSError *error) {
if (error)
{
if ([[self delegate] respondsToSelector:#selector(captureManager:didFailWithError:)])
{
[[self delegate] captureManager:self didFailWithError:error];
}
}
};
if (imageDataSampleBuffer != NULL)
{
NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
UIImage *image = [[UIImage alloc] initWithData:imageData];
if ([self.delegate respondsToSelector:#selector(captureManagerCapturedImage:)])
{
dispatch_async(dispatch_get_main_queue(), ^{
[self.delegate captureManagerCapturedImage:image];
});
}
[library writeImageToSavedPhotosAlbum:[image CGImage]
orientation:(ALAssetOrientation)[image imageOrientation]
completionBlock:completionBlock];
}
else
{
completionBlock(nil, error);
}
if ([[self delegate] respondsToSelector:#selector(captureManagerStillImageCaptured:)])
{
[[self delegate] captureManagerStillImageCaptured:self];
}
}];
}
This code successfully captures an image and saves it to the library. However, at some point while I was working on it, it changed from capturing 5-megapixel 4:3 images to capturing 1920x1080 16:9 images. I can’t find anywhere that the aspect ratio is specified, and I didn’t change any of the code relating to the configuration of the camera, capture sessions, or capture connection. Why did my camera start taking 16:9 photos?
Update: I just re-ran Apple’s original sample code, and it appears that it is also saving 16:9 images captured directly from the video. It is quite possible that I was insane before, or I took a test shot with Camera.app and was looking at that. So my real question is, how do I show a live feed from the camera on the screen while I’m shooting, and take a full-resolution photo. I can’t use UIImagePickerController, because I need to be able to overlay things on top of the live camera feed.
Update 2: I was able to solve this by throwing out the AVCapture code I was using. It turns out that UIImagePickerController does what I needed. I didn’t realize you could overlay custom controls - I thought it took over the whole screen until you were done taking a picture.

Answer 1

If you're capturing frames from a video source, you'll end up with a resolution of 16:9. Capturing frames from a video source and taking photos are different things.