用与显示不同的尺寸捕获照片

Question

我试着用iPhone用AVFoundation捕捉图片，但是我有一些困难要找到我需要的东西。我创建了一个AVCaptureSession并将预设添加到AVCaptureSessionPresetHigh中。self.session.sessionPreset = AVCaptureSessionPresetHigh;

我在视图中显示videoPreviewLayer，我可以用代码捕获图片：

AVCapturePhotoSettings *settings = [AVCapturePhotoSettings photoSettingsWithFormat: @{AVVideoCodecKey:AVVideoCodecJPEG}];
[self.stillImageOutput capturePhotoWithSettings:settings delegate:self]

我得到了一张FHD图片(1920x1080)，所以这个很好。

但现在我想保持一个良好的显示图片，所以保持预设高，但捕获的分辨率640x480。

有可能吗？有什么想法吗？

我试过这个：

NSDictionary *outputSetting = [NSDictionary dictionaryWithObjectsAndKeys:
                               [NSNumber numberWithDouble:1280], (id)kCVPixelBufferHeightKey,
                               [NSNumber numberWithDouble:960], (id)kCVPixelBufferWidthKey,
                               [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA], (id)kCVPixelBufferPixelFormatTypeKey,
                               nil];

AVCapturePhotoSettings *settings = [AVCapturePhotoSettings photoSettingsWithFormat: outputSetting];

[self.stillImageOutput capturePhotoWithSettings:settings delegate:(id)self];

但我知道这个错误：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** +[AVCapturePhotoSettings photoSettingsWithFormat:] Unsupported keys specified: {(
    Height,
    Width
)}. Supported keys are {(
    PixelFormatType
)}'

Answer 1

当您准备拍照时，请求640x480次输出，如下所示：

let settings = AVCapturePhotoSettings()
let pbpf = settings.availablePreviewPhotoPixelFormatTypes[0]
settings.previewPhotoFormat = [
    kCVPixelBufferPixelFormatTypeKey as String : pbpf,
    kCVPixelBufferWidthKey as String : 640,
    kCVPixelBufferHeightKey as String : 480

当您拍照时，将settings传递进来，如下所示：

output.capturePhoto(with: settings, delegate: self)

辅助输出将作为委托方法中的照片的previewCGImageRepresentation返回给您。