如何从AVCaptureSession生成的图像中获取确切的大小框架？

我正在研究一个捕获AVCaptureSession内部特定视图的应用程序，如上图所示。

我使用AVCaptureStillImageOutput来捕获AVCaptureSession中的图像。问题是我得到一个特定大小的图像，（{2448，3264}）。我的解决方案是将该图像转换为我的背景视图的同一帧，以便具有相同的坐标和帧。

使用imageWithImage，我使用了我用于captureView的相同帧，并且一切都很顺利。 resizedImage结束为{768，1024}，它与AVCaptureSession的大小相同。

从这里开始，基于这个坐标，我尝试使用CGImageCreateWithImageInRect基于CaptureView的绿色视图框架来裁剪图像。

我得到的输出图像是关闭的。我的问题是有没有比CGImageCreateWithImageInRect更好的方法来捕获我从AVCaptureSession中获取的图像所需的确切视图？有没有更好的方式去做我想要实现的东西？任何帮助将不胜感激。提前致谢！

AVCaptureConnection *videoConnection = nil; 
    for (AVCaptureConnection *connection in stillImageOutput.connections) { 
     for (AVCaptureInputPort *port in [connection inputPorts]) { 
      if ([[port mediaType] isEqual:AVMediaTypeVideo]) { 
       videoConnection = connection; 

       //Handle orientation for video 

       if(videoConnection.supportsVideoOrientation) 
       { 
        if(captureVideoPreviewLayer.connection.videoOrientation == UIInterfaceOrientationLandscapeLeft){ 
         videoConnection.videoOrientation = AVCaptureVideoOrientationLandscapeLeft; 
        } 
        if(captureVideoPreviewLayer.connection.videoOrientation == UIInterfaceOrientationLandscapeRight){ 
         videoConnection.videoOrientation = AVCaptureVideoOrientationLandscapeRight; 
        } 
        if(captureVideoPreviewLayer.connection.videoOrientation == UIInterfaceOrientationPortrait){ 
         videoConnection.videoOrientation = AVCaptureVideoOrientationPortrait; 
        } 
       } 
       break; 
      } 
     } 
     if (videoConnection) { break; } 
    } 

    NSLog(@"about to request a capture from: %@", stillImageOutput); 
    __weak typeof(self) weakSelf = self; 
    [stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error) { 

     NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer]; 
     UIImage *image = [[UIImage alloc] initWithData:imageData]; 
     UIImage *resizedImage = [weakSelf imageWithImage:image scaledToSize:outputImageView.frame.size]; 

     //Image view to test screenshot of AVCaptureSession 
     outputImageView.image = resizedImage; 

     //Screenshot of captureView frame (green view) 
     CGRect captureFrame = captureView.frame; 

     CGImageRef cropRef = CGImageCreateWithImageInRect(resizedImage.CGImage, captureFrame); 
     UIImage* cropImage = [UIImage imageWithCGImage:cropRef]; 

// Image view to test cropped image 
     sampleImageView.image = cropImage; 

     //Hide Indicator 
     [weakSelf hideActivityView]; 

    }]; 

- (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize { 
    //UIGraphicsBeginImageContext(newSize); 
    // In next line, pass 0.0 to use the current device's pixel scaling factor (and thus account for Retina resolution). 
    // Pass 1.0 to force exact pixel size. 
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0); 
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)]; 
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 
    return newImage; 
}

用于捕获图像的方法。

来源

2017-09-05 Mochi

没有尝试'' AVCaptureVideoPreviewLayer' –

@MikeAlter是的，它是当前设置为AVLayerVideoGravityResizeAspect的videoGravity'。使用AVCaptureStillImageOutput，改变视频重力不会改变我从AVCaptureSession获取的图像的大小。我希望能够将AVCaptureStillImageOutput的框架设置为特定的框架。这行代码“captureVideoPreviewLayer.frame = cameraView.frame;”设置AVCaptureVideoPreviewLayer没有帮助。 – Mochi

我解决了我的问题，通过将像素缩放比例更改为1.0，如评论所述。

- (UIImage *)imageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize { 
    //UIGraphicsBeginImageContext(newSize); 
    // In next line, pass 0.0 to use the current device's pixel scaling factor (and thus account for Retina resolution). 
    // Pass 1.0 to force exact pixel size. 
    UIGraphicsBeginImageContextWithOptions(newSize, NO, 1.0); 
    [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)]; 
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 
    return newImage; 
}

来源

2017-09-05 18:45:35 Mochi

如何从AVCaptureSession生成的图像中获取确切的大小框架？

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