I want to use AVFoundation to set up my own camera feed and process the live feed to detect smiles.
A lot of what I need has been done here: https://developer.apple.com/library/ios/samplecode/SquareCam/Introduction/Intro.html
This code was written a long time back, so I needed to make some modifications to use it the way I want to in terms of appearance.
The changes I made are as follows:
- I enabled auto layout and size classes so as I wanted to support different screen sizes. I also changed the dimensions of the preview layer to be the full screen.
- The session Preset is set to AVCaptureSessionPresetPhoto for iPhone and iPad
- Finally, I set the video gravity to AVLayerVideoGravityResizeAspectFill (this seems to be the keypoint)
Now when I run the application, the faces get detected but there seems to be an error in the coordinates of where the rectangles are drawn
When I change the video gravity to AVLayerVideoGravityResizeAspect, everything seems to work fine again.
The only problem is then, the camera preview is not the desired size which is the full screen.
So now I am wondering why does this happen. I notice a function in square cam: videoPreviewBoxForGravity which processes the gravity type and seems to make adjustments. - (CGRect)videoPreviewBoxForGravity:(NSString *)gravity frameSize:(CGSize)frameSize apertureSize:(CGSize)apertureSize
One thing I noticed here, the frame size stays the same regardless of gravity type.
Finally I read somewhere else, when setting the gravity to AspectFill, some part of the feed gets cropped which is understandable, similar to ImageView's scaletoFill.
My question is, how can I make the right adjustments to make this app work for any VideoGravity type and any size of previewlayer.
I have had a look at some related questions, for example CIDetector give wrong position on facial features seems to have a similar issue but it does not help
Thanks, in advance.