如何改变CIDetector的方向？

Question

所以我试图用Swift中的CIDetector制作一个文本检测器。当我把手机指向一条短信时，它不会检测到。然而，如果我把我的手机转到一边，它就能工作，并检测到文本。我如何改变它，以便它检测到正确的相机方向的文本？这是我的代码：

准备文本检测器功能：

func prepareTextDetector() -> CIDetector {
    let options: [String: AnyObject] = [CIDetectorAccuracy: CIDetectorAccuracyHigh, CIDetectorAspectRatio: 1.0]
    return CIDetector(ofType: CIDetectorTypeText, context: nil, options: options)
}

文本检测功能：

func performTextDetection(image: CIImage) -> CIImage? {
    if let detector = detector {
        // Get the detections
        let features = detector.featuresInImage(image)
        for feature in features as! [CITextFeature] {
            resultImage = drawHighlightOverlayForPoints(image, topLeft: feature.topLeft, topRight: feature.topRight,
                                                        bottomLeft: feature.bottomLeft, bottomRight: feature.bottomRight)                
            imagex = cropBusinessCardForPoints(resultImage!, topLeft: feature.topLeft, topRight: feature.topRight, bottomLeft: feature.bottomLeft, bottomRight: feature.bottomRight)
        }
    }
    return resultImage
}

它的工作方向类似于左边的，但不适合右边的：

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Answer 1

你必须使用CIDetectorImageOrientation，就像苹果在其 documentation中所说的

..。使用CIDetectorImageOrientation选项指定查找直立文本所需的方向。

例如，你需要

let features = detector.featuresInImage(image, options: [CIDetectorImageOrientation : 1]) 

其中，1是exif数，取决于方向，它可以计算如下

func imageOrientationToExif(image: UIImage) -> uint {
    switch image.imageOrientation {
    case UIImageOrientation.Up:
        return 1;
    case UIImageOrientation.Down:
        return 3;
    case UIImageOrientation.Left:
        return 8;
    case UIImageOrientation.Right:
        return 6;
    case UIImageOrientation.UpMirrored:
        return 2;
    case UIImageOrientation.DownMirrored:
        return 4;
    case UIImageOrientation.LeftMirrored:
        return 5;
    case UIImageOrientation.RightMirrored:
        return 7;
    }
}