捕获尺寸与显示尺寸不同的照片 [英] Capture photo with a different dimension than displayed

问题描述

我尝试使用AVFoundation从iPhone捕获图片，但是在寻找所需内容时遇到了一些麻烦. 我创建了一个AVCaptureSession并将预设添加到AVCaptureSessionPresetHigh. self.session.sessionPreset = AVCaptureSessionPresetHigh;

I try to capture picture from a iPhone with AVFoundation but I have some troubles to find what I need. I created a AVCaptureSession and add preset to AVCaptureSessionPresetHigh. self.session.sessionPreset = AVCaptureSessionPresetHigh;

我在视图中显示videoPreviewLayer，并且可以使用以下代码捕获图片:

I display the videoPreviewLayer in my view and I can capture the picture with the code:

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

我得到了FHD图片(1920x1080)，所以效果很好.

And I get a FHD picture (1920x1080), so this works well.

但是现在我要保持良好的显示图片，因此请保持较高的预设值，但要以640x480的分辨率捕获图片.

But now I want to keep a good displayed picture, so keep the preset high but capture picture with the resolution 640x480.

有可能吗? 有什么想法吗?

Is it possible? Any ideas?

我尝试过:

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];

但是我得到这个错误:

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

推荐答案

在准备拍照时，请请求640x480的辅助输出，如下所示:

When you are preparing to take the photo, request a 640x480 secondary output, like this:

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

拍照时，像这样传递settings:

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

在委托方法中，辅助输出将作为照片的previewCGImageRepresentation返回给您.

The secondary output will come back to you as the photo’s previewCGImageRepresentation in the delegate method.

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