####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.
***
####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);
}
```
***
####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];
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