iOS 获取摄像头的每一帧

####序言: 最近公司开始做车牌扫描识别 用到了自定义扫描框和捕获摄像头每一帧转换成图片进行识别. 找了点网上的方法加上自己写的给自己做个总结.

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####视频录制或者拍照可以用UIImagePickerController，不过UIImagePickerController会跳转到系统原生页面.还可以通过另一种方式来获取摄像头数据首先导入 #import 接下来的类需要实现AVCaptureVideoDataOutputSampleBufferDelegate这个协议，只需要实现协议中的一个方法就可以得到摄像头捕获的数据了

```

@property(nonatomic,strong)AVCaptureSession*session;

@property(nonatomic,strong)UIImageView*imageView;

@property(nonatomic,strong)CALayer*customLayer;

@property(nonatomic,strong)AVCaptureVideoPreviewLayer*prevLayer;

- (void)setupCaptureSession

{

NSError*error =nil;

// Create the session

self.session= [[AVCaptureSessionalloc]init];

self.session.sessionPreset=AVCaptureSessionPresetMedium;

AVCaptureDevice*device = [AVCaptureDevice

defaultDeviceWithMediaType:AVMediaTypeVideo];//这里默认是使用后置摄像头，你可以改成前置摄像头

// Create a device input with the device and add it to the session.

AVCaptureDeviceInput*input = [AVCaptureDeviceInputdeviceInputWithDevice:device

error:&error];

if(!input) {

// Handling the error appropriately.

}

[self.sessionaddInput:input];

AVCaptureVideoDataOutput*output = [[AVCaptureVideoDataOutputalloc]init] ;

[self.sessionaddOutput:output];

dispatch_queue_tqueue =dispatch_queue_create("myQueue",NULL);

[outputsetSampleBufferDelegate:selfqueue:queue];

output.videoSettings= [NSDictionarydictionaryWithObjectsAndKeys:

[NSNumbernumberWithInt:kCVPixelFormatType_32BGRA],kCVPixelBufferPixelFormatTypeKey,

[NSNumbernumberWithInt:320], (id)kCVPixelBufferWidthKey,

[NSNumbernumberWithInt:240], (id)kCVPixelBufferHeightKey,

nil];

AVCaptureVideoPreviewLayer* preLayer = [AVCaptureVideoPreviewLayerlayerWithSession:self.session];

preLayer.frame=CGRectMake(0,64,kScreenWidth,kScreenHeight*2/3);

preLayer.videoGravity=AVLayerVideoGravityResizeAspectFill;

[preLayeraddSublayer:self.scanZomeBack.layer];

[self.view.layeraddSublayer:preLayer];

output.minFrameDuration=CMTimeMake(1,15);

[self.sessionstartRunning];

}

- (void)captureOutput:(AVCaptureOutput*)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection{

UIImage*image = [selfimageFromSampleBuffer:sampleBuffer];

NSData* mData =UIImageJPEGRepresentation(image,0.5);

UIImage*PR_image = [UIImageimageWithData:mData];

//NSLog(@"PR_image:%@",PR_image);

[self identifyImage:PR_image];

}

- (UIImage*)imageFromSampleBuffer:(CMSampleBufferRef)sampleBuffer{

CVImageBufferRefimageBuffer =CMSampleBufferGetImageBuffer(sampleBuffer);

CVPixelBufferLockBaseAddress(imageBuffer,0);

void*baseAddress =CVPixelBufferGetBaseAddress(imageBuffer);

size_tbytesPerRow =CVPixelBufferGetBytesPerRow(imageBuffer);

// Get the pixel buffer width and height

size_twidth =CVPixelBufferGetWidth(imageBuffer);

size_theight =CVPixelBufferGetHeight(imageBuffer);

// Create a device-dependent RGB color space

CGColorSpaceRefcolorSpace =CGColorSpaceCreateDeviceRGB();

// Create a bitmap graphics context with the sample buffer data

CGContextRefcontext =CGBitmapContextCreate(baseAddress, width, height,8,

bytesPerRow, colorSpace,kCGBitmapByteOrder32Little|kCGImageAlphaPremultipliedFirst);

// Create a Quartz image from the pixel data in the bitmap graphics context

CGImageRefquartzImage =CGBitmapContextCreateImage(context);

// Unlock the pixel buffer

CVPixelBufferUnlockBaseAddress(imageBuffer,0);

// Free up the context and color space

CGContextRelease(context);

CGColorSpaceRelease(colorSpace);

// Create an image object from the Quartz image

//UIImage *image = [UIImage imageWithCGImage:quartzImage];

UIImage*image = [UIImageimageWithCGImage:quartzImagescale:1.0forientation:UIImageOrientationRight];

// Release the Quartz image

CGImageRelease(quartzImage);

return(image);

}

```

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####其中preLayer是一个预览摄像的界面 .位置什么的也是在preLayer.frame里可设置。你可以在你这个controller中的初始化调用- (void)setupCaptureSession 方法  这样摄像头就开始工作了，摄像头关闭的话 [session stopRunning];