iOS 自定义相机:基础知识储备

            //振动，颤动，摆动
            AudioServicesPlaySystemSound(kSystemSoundID_Vibrate);//            // 播放一下“拍照”的声音，模拟拍照            AudioServicesPlaySystemSound(1108);

// 
- (BOOL)canSwitchCameras {
    return [[AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] count] > 1;
    
}

        _metadataOutput = [[AVCaptureMetadataOutput alloc]init];
        
        [_metadataOutput setMetadataObjectsDelegate:self queue:self.queue];
                [self.videoDataOutput setSampleBufferDelegate:nil queue:self.queue];

// 检测人脸是为了获得“人脸区域”，做“人脸区域”与“身份证人像框”的区域对比，当前者在后者范围内的时候，才能截取到完整的身份证图像
-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection{
    if (metadataObjects.count) {
        AVMetadataMachineReadableCodeObject *metadataObject = metadataObjects.firstObject;
        
        AVMetadataObject *transformedMetadataObject = [self.previewLayer transformedMetadataObjectForMetadataObject:metadataObject];
        CGRect faceRegion = transformedMetadataObject.bounds;
        
        if (metadataObject.type == AVMetadataObjectTypeFace) {
            NSLog(@"是否包含头像：%d, facePathRect: %@, faceRegion: %@",CGRectContainsRect(self.faceDetectionFrame, faceRegion),NSStringFromCGRect(self.faceDetectionFrame),NSStringFromCGRect(faceRegion));
            
            if (CGRectContainsRect(self.faceDetectionFrame, faceRegion)) {// 只有当人脸区域的确在小框内时，才再去做捕获此时的这一帧图像
                // 为videoDataOutput设置代理，程序就会自动调用下面的代理方法，捕获每一帧图像
                if (!self.videoDataOutput.sampleBufferDelegate) {
                    [self.videoDataOutput setSampleBufferDelegate:self queue:self.queue];
                }
            }
        }
    }
}

        _videoDataOutput = [[AVCaptureVideoDataOutput alloc] init];

                    [self.videoDataOutput setSampleBufferDelegate:self queue:self.queue];

#pragma mark - AVCaptureVideoDataOutputSampleBufferDelegate
#pragma mark 从输出的数据流捕捉单一的图像帧
// AVCaptureVideoDataOutput获取实时图像，这个代理方法的回调频率很快，几乎与手机屏幕的刷新频率一样快
-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    if ([self.outPutSetting isEqualToNumber:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange]] || [self.outPutSetting isEqualToNumber:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarFullRange]]) {
        CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
        
        if ([captureOutput isEqual:self.videoDataOutput]) {
            // 身份证信息识别 +(void)iDCardRecognit:(CVImageBufferRef)imageBuffer WithstopRunningBlcok:(void(^)(id make)) stopRunningBlcok finishBlock:(k_finishBlock)finishBlock;
            __weak __typeof__(self) weakSelf = self;

            [KNScanCardManage iDCardRecognit:imageBuffer  WithstopRunningBlcok:^(id  _Nonnull sender) {
                
                            if ([weakSelf.session isRunning]) {
                                [weakSelf.session stopRunning];
                            }

            } finishBlock:weakSelf.finishBlock];//imageBuffer
            
            
            
            
            
            
            // 身份证信息识别完毕后，就将videoDataOutput的代理去掉，防止频繁调用AVCaptureVideoDataOutputSampleBufferDelegate方法而引起的“混乱”
            if (self.videoDataOutput.sampleBufferDelegate) {
                [self.videoDataOutput setSampleBufferDelegate:nil queue:self.queue];
            }
        }
    } else {
        NSLog(@"输出格式不支持");
    }
}

    UITapGestureRecognizer *tapGesture = [[UITapGestureRecognizer alloc]initWithTarget:self action:@selector(focusGesture:)];
    [self.view addGestureRecognizer:tapGesture];