通过cidetector从ciimage获取图像

Question

我正在使用CIDetector来识别矩形。我已经得到了相机，以及显示识别矩形的彩色叠加层。但是，我希望能够从该叠加层（而不是叠加层本身）中获取空间，并且能够仅使用该矩形区域中的图像创建图像视图。

这是我的代码：

import UIKit

class ViewController: UIViewController {



@IBOutlet weak var croppedImg: UIImageView!
     var videoFilter: CoreImageVideoFilter?
var detector: CIDetector?
var image: CIImage?
override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
     var timer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: "update", userInfo: nil, repeats: true)
    // Create the video filter
    videoFilter = CoreImageVideoFilter(superview: view, applyFilterCallback: nil)

    // Simulate a tap on the mode selector to start the process

    if let videoFilter = videoFilter {
        videoFilter.stopFiltering()



        detector = prepareRectangleDetector()
        videoFilter.applyFilter = {
            image in
            return self.performRectangleDetection(image)
        }



        videoFilter.startFiltering()
    }
}




//MARK: Utility methods
func performRectangleDetection(_ image: CIImage) -> CIImage? {
    var resultImage: CIImage?

    if let detector = detector {
        // Get the detections
        let features = detector.features(in: image)
        for feature in features as! [CIRectangleFeature] {
            resultImage = drawHighlightOverlayForPoints(image, topLeft: feature.topLeft, topRight: feature.topRight,
                                                        bottomLeft: feature.bottomLeft, bottomRight: feature.bottomRight)
        }
    }

    return resultImage

}

/* func performQRCodeDetection(_ image: CIImage) -> (outImage: CIImage?, decode: String) {
    var resultImage: CIImage?
    var decode = ""
    if let detector = detector {
        let features = detector.features(in: image)
        for feature in features as! [CIQRCodeFeature] {
            resultImage = drawHighlightOverlayForPoints(image, topLeft: feature.topLeft, topRight: feature.topRight,
                                                        bottomLeft: feature.bottomLeft, bottomRight: feature.bottomRight)
            decode = feature.messageString!
        }
    }
    return (resultImage, decode)
}*/

func prepareRectangleDetector() -> CIDetector {
    let options: [String: Any] = [CIDetectorAccuracy: CIDetectorAccuracyHigh, CIDetectorAspectRatio: 1.0]
    return CIDetector(ofType: CIDetectorTypeRectangle, context: nil, options: options)!
}

/* func prepareQRCodeDetector() -> CIDetector {
    let options = [CIDetectorAccuracy: CIDetectorAccuracyLow]
    return CIDetector(ofType: CIDetectorTypeQRCode, context: nil, options: options)!
}*/

func drawHighlightOverlayForPoints(_ image: CIImage, topLeft: CGPoint, topRight: CGPoint,
                                   bottomLeft: CGPoint, bottomRight: CGPoint) -> CIImage {

    var overlay = CIImage(color: CIColor(red: 0.0, green: 0.4, blue: 0.6, alpha: 0.5))

    overlay = overlay.cropping(to: image.extent)
    overlay = overlay.applyingFilter("CIPerspectiveTransformWithExtent",
                                     withInputParameters: [
                                        "inputExtent": CIVector(cgRect: image.extent),
                                        "inputTopLeft": CIVector(cgPoint: topLeft),
                                        "inputTopRight": CIVector(cgPoint: topRight),
                                        "inputBottomLeft": CIVector(cgPoint: bottomLeft),
                                        "inputBottomRight": CIVector(cgPoint: bottomRight)
        ])
   /* if resultImage != nil{
        croppedImg.image = UIImage(ciImage: resultImage!)
        croppedImg.frame = (image.extent)
        croppedImg.layer.borderWidth = 8
        croppedImg.layer.borderColor = UIColor.red.cgColor
    }*/
    return overlay.compositingOverImage(image)
}
func update() {
    // Something cool
   // if resultImage != nil{
    //croppedImg.image = UIImage(ciImage: (resultImage)!)
   // }


 }


}

裁剪图像是屏幕一角的较小图像，我只想显示检测到的矩形。