objective-c - 将检测到的矩形从纵向 CIImage 转换为横向 CIImage

Question

我正在修改找到的代码 here .在代码中，我们使用 AVCaptureSession 从手机摄像头捕获视频，并使用 CIDetector 检测图像馈送中的矩形。提要有一个 640x842 的图像(纵向的 iphone5)。然后，我们在图像上进行叠加，以便用户可以看到检测到的矩形(实际上它大部分时间是梯形)。

当用户按下 UI 上的按钮时，我们会从视频中捕获图像，然后在这张较大的图像 (3264x2448) 上重新运行矩形检测，如您所见，它是横向的。然后我们对检测到的矩形进行透视变换并裁剪图像。

这工作得很好，但我遇到的问题是，五分之一捕获较大图像上检测到的矩形与从较小图像检测到(并呈现给用户)的矩形不同。尽管我只在检测到手机(相对)静止时才进行拍摄，但最终图像并不代表用户期望的矩形。

为了解决这个问题，我的想法是使用最初捕获的矩形的坐标并将它们转换为捕获的静止图像上的矩形。这就是我挣扎的地方。

我用检测到的矩形试了一下:

CGFloat radians = -90 * (M_PI/180);
CGAffineTransform rotation = CGAffineTransformMakeRotation(radians);

CGRect rect = CGRectMake(detectedRect.bounds.origin.x, detectedRect.bounds.origin.y, detectedRect.bounds.size.width, detectedRect.bounds.size.height);

CGRect rotatedRect = CGRectApplyAffineTransform(rect, rotation);

所以给定一个检测到的矩形:

左上:88.213425, 632.31329右上角:545.59302、632.15546右下角:575.57819、369.22321左下角:49.973862、369.40466

我现在有了这个旋转的矩形:

原点 = (x = 369.223206, y = -575.578186)尺寸=(宽度=263.090088，高度=525.604309)

如何将较小肖像图像中旋转的矩形坐标转换为 3264x2448 图像的坐标？

编辑呃..阅读我自己的方法后意识到从梯形创建矩形不会解决我的问题!

检测矩形等的支持代码...

// In this method we detect a rect from the video feed and overlay

-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)CMSampleBufferGetImageBuffer(sampleBuffer);

    CIImage *image = [CIImage imageWithCVPixelBuffer:pixelBuffer];

   // image is 640x852 on iphone5

    NSArray *rects = [[CIDetector detectorOfType:CIDetectorTypeRectangle context:nil options:@{CIDetectorAccuracy : CIDetectorAccuracyHigh}] featuresInImage:image];

    CIRectangleFeature *detectedRect = rects[0]; 

    // draw overlay on image code....
}

这是如何获取静止图像的总结版本:

// code block to handle output from AVCaptureStillImageOutput
[self.stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error)
     {
         NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
         CIImage *enhancedImage = [[CIImage alloc] initWithData:imageData options:@{kCIImageColorSpace:[NSNull null]}];
             imageData = nil;

         CIRectangleFeature *rectangleFeature = [self getDetectedRect:[[self highAccuracyRectangleDetector] featuresInImage:enhancedImage]];

         if (rectangleFeature) {
             enhancedImage = [self   correctPerspectiveForImage:enhancedImage withTopLeft:rectangleFeature.topLeft andTopRight:rectangleFeature.topRight andBottomRight:rectangleFeature.bottomRight andBottomLeft:rectangleFeature.bottomLeft];
         }
    }

谢谢。

Answer 1

我在做这类事情时遇到了同样的问题。我已经通过快速执行以下代码解决了它。看看能不能帮到你。

 if let videoConnection = stillImageOutput.connection(withMediaType: AVMediaTypeVideo) {
            stillImageOutput.captureStillImageAsynchronously(from: videoConnection) {
                (imageDataSampleBuffer, error) -> Void in
                let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(imageDataSampleBuffer)
                var img = UIImage(data: imageData!)!

                let outputRect = self.previewLayer?.metadataOutputRectOfInterest(for: (self.previewLayer?.bounds)!)
                let takenCGImage = img.cgImage
                let width = (takenCGImage?.width)!
                let height = (takenCGImage?.height)!
                let cropRect = CGRect(x: (outputRect?.origin.x)! * CGFloat(width), y: (outputRect?.origin.y)! * CGFloat(height), width: (outputRect?.size.width)! * CGFloat(width), height: (outputRect?.size.height)! * CGFloat(height))
                let cropCGImage = takenCGImage!.cropping(to: cropRect)
                img = UIImage(cgImage: cropCGImage!, scale: 1, orientation: img.imageOrientation)

                let cropViewController = TOCropViewController(image: self.cropToBounds(image: img))
                cropViewController.delegate = self
                self.navigationController?.pushViewController(cropViewController, animated: true)
            }
        }