1、最后獲得的圖像反向轉(zhuǎn)換

int height = CVPixelBufferGetHeight(pixelBuffer);
CGAffineTransform transform = CGAffineTransformMakeScale(1, -1);
transform = CGAffineTransformTranslate(transform, 0, -1 * height);
/* Do your face detection */
CGRect faceRect = CGRectApplyAffineTransform(feature.bounds, transform);
CGPoint mouthPoint = CGPointApplyAffineTransform(feature.mouthPosition, transform);

2、如果圖像一開(kāi)始就不是正向的

/**
  *   問(wèn)題來(lái)自 UIImage 的取向和 CIDetectorImageOrientation 之間的區(qū)別。從 iOS 的文檔：
     CIDetectorImageOrientation

     要檢測(cè)密鑰被用來(lái)指定圖像的顯示方向的功能。此密鑰是一個(gè) NSNumber 對(duì)象具有相同的值定義的 TIFF 和 EXIF 規(guī)格 ；值的范圍可以從 1 到 8。值指定原點(diǎn) (0，0) 的圖像所在的位置。如果不存在，默認(rèn)值是 1，這意味著圖像的原點(diǎn)是左上角。每個(gè)值所指定的圖像來(lái)源的詳細(xì)信息，請(qǐng)參閱 kCGImagePropertyOrientation。

     可用在 iOS 5.0 和更高版本。

     在 CIDetector.h 中聲明。
     
     所以現(xiàn)在的問(wèn)題是這些兩個(gè)方向之間的轉(zhuǎn)換，在這里是我的代碼中的所作所為、 我測(cè)試和它為所有方向工作：
  *
  */

    int exifOrientation;

    switch (image.imageOrientation) {

        case UIImageOrientationUp: {
  
            exifOrientation = 1;
            break; 
        }

        case UIImageOrientationDown: {
          
            exifOrientation = 3;
            break;
        }

        case UIImageOrientationLeft: {
          
            exifOrientation = 8;
            break;
        }

        case UIImageOrientationRight: {
          
            exifOrientation = 6;
            break;
        }

        case UIImageOrientationUpMirrored: {
         
            exifOrientation = 2;
            break;
        }

        case UIImageOrientationDownMirrored: {
          
            exifOrientation = 4;
            break;
        }

        case UIImageOrientationLeftMirrored: {
          
            exifOrientation = 5;
            break;
        }

        case UIImageOrientationRightMirrored: {
            
            exifOrientation = 7;
            break;
        }
    }

    NSDictionary *detectorOptions = @{ CIDetectorAccuracy : CIDetectorAccuracyHigh }; 
// TODO: read doc for more tuneups

    CIDetector *faceDetector = [CIDetector detectorOfType:CIDetectorTypeFace context:nil options:detectorOptions];

    NSArray *features = [faceDetector featuresInImage:[CIImage imageWithCGImage:image.CGImage]
                                              options:@{CIDetectorImageOrientation:[NSNumber 
                                                                                    numberWithInt:exifOrientation]}];