Question

我正在开发一个iOS应用程序，我需要进行一些对象实时扫描。为此，我需要在示例中每秒采用3或4帧。这是我创建捕获会话的代码：

// Create an AVCaptureSession
    AVCaptureSession *captureSession = [[AVCaptureSession alloc] init];
    captureSession.sessionPreset = AVCaptureSessionPresetHigh;

    // Find a suitable AVCaptureDevice
    AVCaptureDevice *photoCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

    // Create and add an AVCaptureDeviceInput
    NSError *error = nil;
    AVCaptureDeviceInput *videoInput = [AVCaptureDeviceInput deviceInputWithDevice:photoCaptureDevice error:&error];
    if(videoInput){
        [captureSession addInput:videoInput];
    }

    // Create and add an AVCaptureVideoDataOutput
    AVCaptureVideoDataOutput *videoOutput = [[AVCaptureVideoDataOutput alloc] init];
    // we want BGRA, both CoreGraphics and OpenGL work well with 'BGRA'
    NSDictionary *rgbOutputSettings = [NSDictionary dictionaryWithObject:
                                       [NSNumber numberWithInt:kCMPixelFormat_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
    [videoOutput setVideoSettings:rgbOutputSettings];

    // Configure your output, and start the session
    dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
    [videoOutput setSampleBufferDelegate:self queue:queue];

    if(videoOutput){
        [captureSession addOutput:videoOutput];
    }

    [captureSession startRunning];


    // Setting up the preview layer for the camera
    AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:captureSession];
    previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
    previewLayer.frame = cameraViewCanvas.bounds;

    // ADDING FINAL VIEW layer TO THE MAIN VIEW sublayer
    [cameraViewCanvas.layer addSublayer:previewLayer];

并且在队列上调用委托方法：

-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection{
    if(isCapturing){
        NSLog(@"output");

        CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
        CFDictionaryRef attachments = CMCopyDictionaryOfAttachments(kCFAllocatorDefault, sampleBuffer, kCMAttachmentMode_ShouldPropagate);
        CIImage *ciImage = [[CIImage alloc] initWithCVPixelBuffer:pixelBuffer options:(NSDictionary *)attachments];

        UIImage *newFrame = [[UIImage alloc] initWithCIImage:ciImage];
        [self showImage:newFrame];
    }
}

问题是我无法在屏幕上看到图像，没有错误和警告，但图像未显示。我的问题是 - 我是否在正确的道路上，需要在我的代码中修复哪些内容才能在屏幕上显示图像？

Answer 1

迟来的，但问题可能是由于未在主线程中设置图像（captureOutput在您创建的单独的调度队列中调用，最有可能）。

dispatch_async(dispatch_get_main_queue(), ^{
  [self showImage:newFrame];
});

或

[self performSelectorOnMainThread:@selector(showImage:) newFrame waitUntilDone:YES];

相机实时扫描iOS

1 个答案: