ios - 使用photooutput抓图，图片大小随机变化

Question

使用 iPhone XS 进行测试，sessionPreset设置为照片。图片分辨率通常为 4032x3024，但有时以 3088x1938 拍摄。什么原因？

下面是我的代码。

let photoSettings = AVCapturePhotoSettings(format: [kCVPixelBufferPixelFormatTypeKey as String: Int(kCVPixelFormatType_32BGRA)])
photoSettings.isHighResolutionPhotoEnabled = true
photoSettings.isAutoStillImageStabilizationEnabled = true
photoSettings.flashMode = self.flashMode
self.photoOutput.capturePhoto(with: photoSettings, delegate: self)