AVCapturePhotoOutput自定义简单相机

在iOS 10之前，自定义相机一般使用AVCaptureStillImageOutput实现。但是AVCaptureStillImageOutput在iOS 10以后被弃用了。

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所以我们来使用AVCapturePhotoOutput来实现自定义简单相机，AVCapturePhotoOutput 的功能自然会更加强大，不仅支持简单JPEG图片拍摄，还支持Live照片和RAW格式拍摄。

使用：
首先初始化：按照需要参数初始化就行了，和AVCaptureStillImageOutput差别不大。直接上代码：

    self.session = [AVCaptureSession new];
    [self.session setSessionPreset:AVCaptureSessionPresetHigh];
    
    NSArray *devices = [NSArray new];
    devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices) {
        if (isBack) {
            if ([device position] == AVCaptureDevicePositionBack) {
                _device = device;
                break;
            }
        }else {
            if ([device position] == AVCaptureDevicePositionFront) {
                _device = device;
                break;
            }
        }
    }
    
    NSError *error;
    self.input = [[AVCaptureDeviceInput alloc] initWithDevice:self.device error:&error];
    if ([self.session canAddInput:self.input]) {
        [self.session addInput:self.input];
    }
    
    self.imageOutput = [[AVCapturePhotoOutput alloc] init];
    NSDictionary *setDic = @{AVVideoCodecKey:AVVideoCodecJPEG};
    _outputSettings = [AVCapturePhotoSettings photoSettingsWithFormat:setDic];
    [self.imageOutput setPhotoSettingsForSceneMonitoring:_outputSettings];
    [self.session addOutput:self.imageOutput];
    self.preview = [[AVCaptureVideoPreviewLayer alloc] initWithSession:self.session];
    [self.preview setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    [self.preview setFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
    [self.layer addSublayer:self.preview];
    [self.session startRunning];

实现照片获取：
AVCaptureStillImageOutput中使用captureStillImageAsynchronouslyFromConnection 在bolck中直接可以获取到图片，AVCapturePhotoOutput需要实现AVCapturePhotoCaptureDelegate协议，在协议中获取。
获取当前屏幕图片输出：

[self.imageOutput capturePhotoWithSettings:_outputSettings delegate:self];

实现AVCapturePhotoCaptureDelegate协议，并在didFinishProcessingPhotoSampleBuffer方法中获取图片：

- (void)captureOutput:(AVCapturePhotoOutput *)captureOutput didFinishProcessingPhotoSampleBuffer:(nullable CMSampleBufferRef)photoSampleBuffer previewPhotoSampleBuffer:(nullable CMSampleBufferRef)previewPhotoSampleBuffer resolvedSettings:(AVCaptureResolvedPhotoSettings *)resolvedSettings bracketSettings:(nullable AVCaptureBracketedStillImageSettings *)bracketSettings error:(nullable NSError *)error {
    
    NSData *data = [AVCapturePhotoOutput JPEGPhotoDataRepresentationForJPEGSampleBuffer:photoSampleBuffer previewPhotoSampleBuffer:previewPhotoSampleBuffer];
    UIImage *image = [UIImage imageWithData:data];
    
    UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
}

这样就获取到图片了。
最后附Demo

AVCapturePhotoOutput自定义简单相机

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