前传 - AVCaptureStillImageOutput
捕获照片-AVCaptureStillImageOutput
在iOS中捕捉静态拍摄画面，可以通过很多方式，像是通过UIImagePickerController的方式，调用系统提供的API来捕捉画面，或是通过AVFoundation提供的AVCaptureStillImageOutpu或AVCapturePhotoOutput来捕捉画面。而本篇文章所采用的方法属于后者通过AVFoundation来实现拍照。
AVCaptureStillImageOutput
AVCaptureStillImageOutput是AVCaptureOutput具体子类，用来拍摄静态照片，该类在iOS 10.中已弃用，不支持较新的相机拍照功能，如RAW图像输出和动态照片。在iOS 10.0及更高版本中改用AVCapturePhotoOutput类。
- 拍照
调用下述方法拍照:
- (void)captureStillImageAsynchronouslyFromConnection:(AVCaptureConnection *)connection
completionHandler:(void (^)(CMSampleBufferRef imageDataSampleBuffer, NSError *error))handler;
参数：
- connection: 从中捕获图像的连接。
- handler: 捕获图像后要调用的块，块参数如下：
imageDataSampleBuffer: 捕获的数据
error: 如果请求失败，返回NSError对象，否则返回nil
可以使用下述属性查看是否正在拍照：
@property(readonly, getter=isCapturingStillImage) BOOL capturingStillImage;
- 图像输出设置
@property(nonatomic, copy) NSDictionary<NSString *, id> *outputSettings;
当前仅支持AVVideoCodecKey和kCVPixelBufferPixelFormatTypeKey 可以使用 -availableImageDataCVPixelFormatTypes 和 -availableImageDataCodecTypes 获取支持的codec keys 和 pixel formats
- availableImageDataCVPixelFormatTypes
支持的图像格式，可以将其作用在outputSettings中kCVPixelBufferPixelFormatTypeKey的值 - availableImageDataCodecTypes:
支持的图像编解码格式，可以将其作用在outputSettings中AVVideoCodecKey的值
- 图像格式转换
将静态图像数据CMSampleBufferRef转为NSData
+ (NSData *)jpegStillImageNSDataRepresentation:(CMSampleBufferRef)jpegSampleBuffer;
- jpegSampleBuffer: 携带 JPEG 图像数据的样本缓冲区，如果jpegSampleBuffer为 NULL 或不是JPEG 格式，则此方法抛出异常NSInvalidArgumentException。
- 设置拍照方向
如果程序只支持纵向，但是如果用户横向拍照时，需要调整结果照片的方向
//判断是否支持设置视频方向
@property(nonatomic, readonly, getter=isVideoOrientationSupported) BOOL supportsVideoOrientation;
设置照片方向:
// 获取连接
AVCaptureConnection *connection = [self.imageOutput connectionWithMediaType:AVMediaTypeVideo];
//程序只支持纵向，但是如果用户横向拍照时，需要调整结果照片的方向
// 判断是否支持设置视频方向
if (connection.isVideoOrientationSupported) {
connection.videoOrientation = [self currentVideoOrientation];
}
[self.imageOutput captureStillImageAsynchronouslyFromConnection:connection completionHandler:^(CMSampleBufferRef _Nullable imageDataSampleBuffer, NSError * _Nullable error) {
if (imageDataSampleBuffer != NULL) {
NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
UIImage *image = [[UIImage alloc] initWithData:imageData];
[self writeImageToAssetsLibrary:image];
} else {
NSLog(@"NULL imageDataSampleBuffer: %@", error.localizedDescription);
}
}];
// 获取方向值
- (AVCaptureVideoOrientation)currentVideoOrientation {
AVCaptureVideoOrientation orientation;
switch (UIDevice.currentDevice.orientation) {
case UIDeviceOrientationPortrait:
orientation = AVCaptureVideoOrientationPortrait;
break;
case UIDeviceOrientationLandscapeRight:
orientation = AVCaptureVideoOrientationLandscapeLeft;
break;
case UIDeviceOrientationPortraitUpsideDown:
orientation = AVCaptureVideoOrientationPortraitUpsideDown;
break;
default:
orientation = AVCaptureVideoOrientationLandscapeRight;
break;
}
return orientation;
}
- 实例
AVCaptureStillImageOutput *myStillImageOutput = [[AVCaptureStillImageOutput alloc] init];
myStillImageOutput.outputSettings = @{AVVideoCodecKey: AVVideoCodecTypeJPEG};
今生 - AVCapturePhotoOutput
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。
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。
